WordPress.com · Web view1.01use the following units: kilogram (kg), metre (m), metre/second (m/s),...

Year 10

Edexcel Science

iGCSE Physics

I. Work, Power and Acceleration

2019-2020

Name:________________

Physics Teacher:______________

House

CG

Specification Checklist

1.01use the following units: kilogram (kg), metre (m), metre/second (m/s), metre/second2 (m/s2), newton (N), second (s) and newton/kilogram (N/kg)

1.11describe the effects of forces between bodies such as changes in speed, shape or

direction

1.12identify different types of force such as gravitational or electrostatic

1.13understand how vector quantities differ from scalar quantities

1.14understand that force is a vector quantity

1.17know and use the relationship between unbalanced force, mass and acceleration:

force = mass × acceleration

F = m × a

1.21describe the forces acting on falling objects (and explain why falling objects reach a

terminal velocity)

4.03use the principle of conservation of energy

4.11know and use the relationship between work done, force and distance moved in the

direction of the force:

work done = force × distance moved

W = F × d

4.12know that work done is equal to energy transferred

4.16describe power as the rate of transfer of energy or the rate of doing work

4.17use the relationship between power, work done (energy transferred) and time taken:

Power = work done/time taken

Key Definitions

Key Word

Image

Definition

Acceleration

The rate of change of speed.

Balanced Force

The forces on an object that cancel each other out. No resultant force.

Drag

A general term for all types of friction on a moving object.

Joule

Unit of Energy

Power

The rate of energy transfer (work done per second).

Resultant Force

The remaining force on an object after all the individual forces have been added and subtracted from each other.

Scalar

Something with only magnitude. Just a number.

Terminal Velocity

The maximum speed of an object. When the drag and the propelling force are balanced.

Unbalanced Force

The forces on an object do not cancel out. A resultant force is produced.

Vector

Something with magnitude and direction

Watt

Unit of Power

Work Done

The energy used to move an object a certain distance.

1: Work Done

Forces Recap Quiz

Use the knowledge you have gained in previous lessons to answer the following questions:

1. What is the mass of an object that weighs 562N?

………………………………………………………………(2)

2. State Hooke’s Law

…………………………………………………………………………………………………………………………………………………………………………………… (1)

3. Calculate the resultant forces on the objects below:

[4]

4. A cyclist is accelerating down a hill. What can you say about the forces on the bike?…………………………………………………………………………………………………………………………………………………………………………………… (2)

5. What is the ‘centre of gravity’?…………………………………………………………………………………………………………………………………………………………………………………… (1)

6. Draw a force- extension graph for an object which behaves elastically.

(3)

7. Calculate the acceleration of a car that moves from 10 m/s to 22 m/s in 4 seconds.

(3)

Score [ /13]

Learning Outcomes:

1. Describe the difference between a scalar and a vector

2. Rearrange and use the formula:

3. Know that work done is equal to energy transferred.

Vectors vs. Scalars

Examples

Vector

Scalar

Key Ideas

1. Scalars are quantities that only have magnitude (size).

2. Vectors are quantities that have magnitude (size) and direction.

3. Force is a vector quantity.

4. We can represent Force as an arrow on a diagram to illustrate direction and size (length).

Work Done

Key Ideas

1. Work done, force and distance travelled are linked in the equation

2. To use the equation the force must be acting in the same direction as the way the object is moving

3. Work done is equal to the energy transferred.

Worked Examples

1. A man lifts a parcel weighing 5 N from the ground on to a shelf 2 metres high. How much work does he do on the parcel?

2. James exerts a horizontal force of 50N on a box which moves horizontally 11m. Calculate the work done.

Worksheet – Work Done

Complete the questions below using the equation you have just learnt. You must show all of your working [equation, substitution, solution and units]

1. What is the work done if we apply a 1.2N force and we move 4 m in the direction of force?

…………………..

2. What is the work done if we apply a 7N force and we move 8 m in the direction of the force?

…………………..

3. What is the work done when a force of 5 N is applied to a ball and it moves 80 m?

…………………..

4. What distance is moved if we have an 8N force and the work done is 90 J?

…………………..

5. What is the distance moved if we have a 70N force and work done is 8 J?

…………………..

6. What force is required to move 19 m if the work done is 9 J?

…………………..

7. What force is required to move 7 m if the work done is 21 J?

…………………..

8. A crane lifts a weight of 30kN through a height of 20m. Calculate the work done.

…………………..

9. A dog pulls a sledge by applying a force of 10N through a distance of 1.5km. Calculate the work done.

…………………..

10. 600kJ of work is done when a box is moved through a distance of 20m. Calculate the force required to do this work on the box.

…………………..

11. 12MJ of work is done to lift a 500N object. Calculate how high it was lifted.

…………………..

12. How much work is done when a 20kg crate is move through a distance of 1km by applying a constant force of 20mN?

…………………..

13. How far can an object be pushed if a force of 2MN is applied and 8kJ of energy is transferred to the object.

…………………..

14. A man is carrying a box. How much work is done as the man walks 100m forward if the box has weight of 12N?

…………………..

2: Power

Work Done Calculations

Use the knowledge you have gained in the previous lesson to answer the following questions:

1. What force is required to move a box 8m if the work done is 550J?

………………….. (3)

2. How much work is done if a person weighing 750N climbs a 7m ladder?

………………….. (3)

3. If you transfer 9kJ of energy to an object using a force of 35N, how far will the object move?

………………….. (3)

4. A box has a mass of 5kg. How much work has to be done to lift the box 2m off the ground?

………………….. (3)

Score [ /12]

Learning Outcomes:

1. Rearrange and use the equation:

2. Define power as the rate of work done.

3. Take measurements to calculate the power output of a person.

Power

Key Ideas

1. Power, work done and time are linked in the equation:

2. We can define power as the rate of work done or the rate of energy transferred.

3. Work done is equal to the energy transferred.

4. Power is measured in Watts

Worked Examples

1. A crane does 1000J of work in 30s. What is the power output by the crane?

2. An electrical lamp is marked as 100W. How many joules of electrical energy are transformed into light and heat in 1 minute?

Worksheet – Power


1. Work out the power if the energy is 1200J and the time is 12s.

…………………..

2. Calculate the power if the time is 30s and the energy is 9000J

…………………..

3. 1200J of work is done when a parcel is moved on a conveyer belt. It takes 2 seconds to move the parcel. Calculate the power

…………………..

4. Calculate the work done if the power is 30W and the time is 120s.

…………………..

5. Calculate the energy transferred if the time is 2 minutes and the power is 50W.

…………………..

6. How much work is done if the output power over 20s is 6000W.

…………………..

7. Calculate the time if the energy is 2000J and the power is 25W.

…………………..

8. How long will it take a crane with an output power of 8500W to do 50 000J of work?

…………………..

9. How long will it take a robotic arm with a power output of 750W to transfer 4500J of energy?

…………………..

10. 600kJ of work is done when a box is moved though a distance of 200m in 100s. Calculate the power.

…………………..

11. A dog team pulls a sledge of mass 100kg through a distance of 2km in 10 minutes applying and average force of 100N. Calculate the power.

…………………..

12. Calculate the power when a 20kg crate is move through a distance of 1km in 20 minutes applying a constant force of 25N.

…………………..

13. How long will it take a machine with a power output of 75kW to transfer 200MJ of energy?

…………………..

14. 430MJ of work is done when a new car is moved on a conveyer belt. It takes 2 minutes to move the parcel. Calculate the power

…………………..

I1: Investigating Power Output

Health and Safety Check!

I will be sensible on the stairs to avoid injury by falling

In this investigation you are going to measure how yourpower output as you climb a set of stairs.

What are the two equations you have learnt in the topicso far?

During the investigation you will be calculating your Work Done. On the diagram below label the direction of the force you are applying (to overcome your weight) and thus the distance you will need to measure to calculate work done.

In a different colour can you annotate the distance you will need to measure to figure out your average speed.

Method:

1. Measure your weight using the Newton Scales

2. Measure the height of the stairs you will be climbing. [Tip: Measure the height of 1 step and multiply that by the number of steps on the staircase]

3. Measure the distance you will be walking [This will need to be done using a measuring tape]

4. Have someone time how long it takes you to walk up the stairs.

5. Repeat step 4 for five different paces (walking initially, get a bit faster each time).

6. Fill times into the results table

7. Use your results to calculate your:

a. Average speed

b. Work done

c. Power

Results

Height of Stairs [ ]

Distance Travelled [ ]

Weight [ ]

Time [s]

Average speed [m/s]

Work Done [J]

Power Output [W]

Plot both sets of results below (power output on the y-axis, average speed on the x-axis).

Conclusions

Use your results/graph to answer the following questions.

1. What was the relationship between average speed and power output?………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

2. In what direction was your weight acting during the investigation? ……………………………………………………………………………………………

3. Why did we only need the height of the stairs to calculate work done?…………………………………………………………………………………………………………………………………………………………………………………………

4. How would you have changed the method if you were only able to measure your mass with a balance?………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

5. How would you expect the size of a person to affect their power output?………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

6. What would the power output have been if you had climbing a vertical ladder next to the staircase to the same height? Explain your answer. ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

7. If we had done this experiment climbing down the stairs instead, how much work would be have done? Explain your answer. ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

3: Newton’s 2nd Law

Knowledge and Understanding Quiz

Use the knowledge you have gained in the previous lessons to answer the following questions:

1. What are the units of Power?

…………………………………………………………………………………………… (1)

2. What are the units of Work Done?

…………………………………………………………………………………………… (1)

3. How much energy does a 690N person transfer if they climb an 11m ladder?

………………….. (3)

4. A box has a mass of 5kg. How much work has to be done to move the box 5m to the left?

………………….. (3)

5. What is the power output of a crane which lifts a 100kg box 25m in 1 minute?

………………….. (3)

Score [ /10]

Learning Outcomes:

1. Rearrange and use the equation:

2. Describe Newton’s 2nd Law of motion

3. Investigate the effects of mass/unbalanced force on the acceleration of an object

Force, Mass and Acceleration

Key Ideas

1. An object will not change its velocity unless an unbalanced force acts upon it.

2. Force, mass and acceleration are linked in the equation:

3. This means that if the same unbalanced force was applied to two objects of different masses. The object with the smaller mass would accelerate more.

Worked Examples

1. What unbalanced force is required to accelerate a 6kg mass by 2m/s2?

2. An object experiences an unbalanced force of 16N and accelerates at 4m/s2. What must the mass of the object have been?

Worksheet – Newton’s 2nd Law


1. How much force is required to accelerate a 2 kg mass at 3 m/s2?

…………………..


…………………..


…………………..

4. Given a force of 100 N and an acceleration of 10 m/s2, what is the mass?

…………………..


…………………..

6. What is the acceleration of a 10 kg mass pushed by a 5 N force?

…………………..


…………………..

8. What is the acceleration of an 18 kg mass pushed by a 9 N force?

…………………..

9. Find the acceleration of the 2 kg block in the following diagram.

…………………..

10. Find the acceleration of the 500g block in the following diagram

…………………..

11. If a 600g object is accelerating at 2m/s2, what is the unbalanced force acting on it?

…………………..

12. Given a force of 560 kN and an acceleration of 3 m/s2, what is the mass?

…………………..

13. How much force is required to accelerate a 50 g mass at 25 m/s2?

…………………..

I2: Investigating Newton’s 2nd Law


I will ensure the trolley isstopped safely

In this investigation you are going to be investigating Newton’s 2nd Law of motion.

There are two different versions of this investigation.

1. Effects of mass on acceleration

2. Effects of unbalanced force on acceleration.

Circle/highlight the investigation you will be doing.

Method

1. Set up the apparatus as shown in the diagram below.

2. Programme the light gates (as shown by your teacher) to measure the acceleration of the object.

3. Set the height of the ramp to 15cm.

4. Add your independent variable to the results table on the next page.

5. Add 1kg of mass to the weight hanger

6. Add masses to the trolley to the value of 100g.

7. Add masses to the weight hander to the value of 100g

8. Start the data logger before letting trolley go.

9. Release trolley and record results in the results table

10. Repeat steps 5, 6, 8 and 9 for different masses on the trolley (100g intervals)

11. Repeat steps 7-9 for different masses on the hanger (100g intervals)

12. Plot relevant graph.

Results

Acceleration [ ]

Plot your results on the graph below (acceleration on the y-axis)

Describe the relationship in your graph above.

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

4: Terminal Velocity

Revision Calculations

Identify the correct equation to use to answer the following questions.

1. What is the acceleration of an object of mass 5kg if it feels a resultant force of 60N?

………………….. (3)

2. What is the power output of an object which transfers 500J of energy is 20s?

………………….. (3)

3. How long will it take a car to transfer 10kJ of energy if its power output is 1000W?

………………….. (3)

4. How much energy is transferred when you raise a 600g object by 3m?

………………….. (3)

5. A car starts from rest and accelerates at 2.5 m/s2 during which it covers a distance of 300 m. What is the final speed of the car?

………………….. (3)

Score [ /15]

Learning Outcomes:

1. Define the term ‘terminal velocity’

2. Explain why an object reaches terminal velocity.

3. Describe an investigation to measure the terminal velocity of an object.

Terminal Velocity

Key Ideas

1. At the point of release the only force acting on an object is weight.

2. This unbalanced force causes the object to accelerate

3. As the object accelerates the drag force begins to increase

4. As the object gains speed the drag force increases

5. Eventually the drag force is equal in magnitude to weight and the forces are balanced.

6. This causes the object to travel at a constant speed which we call terminal velocity.

I3: Plotting Terminal Velocity


Keep neodymium magnetaway from electronics

In this demonstration you will work as a group to plotthe motion of a ball falling through viscous liquid.

The tube will be split into sections.

You will be measuring the time it takes the ball to fall through section _________.

The distance between each of the sections is _____________.

We can then calculate the objects velocity using the following equation:

How will we know if the object has reached terminal velocity?

……………………………………………………………………………………………………………

Method/Diagram

Results

Section

Time [s]

Velocity [m/s]

Timer 1

Timer 2

Average

1

2

3

4

5

6

7

8

9

10

11

12

13

Plot your results on the graph below (distance on the x-axis, velocity on the y-axis)

I4: Surface Area and Terminal Velocity


Keep neodymium magnetaway from electronics

In this investigation you are going to investigate how the surface area of an object affects its terminalvelocity.

You will be using a number of different metal spheres.

What shape is the cross sectional area of a sphere? _________________

How will you measure and calculate the maximum cross sectional area of your sphere?

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………

Method

1. Measure and calculate the maximum cross sectional area of each of your spheres using your method above.

2. Fill your measuring cylinder with a viscous liquid (leaving 5cm empty at the top of the measuring cylinder

3. Put two markings on your cylinder with board marker as per the diagram below

4. Measure the distance between your markings.

5. Drop your ball into the liquid and time how long it takes the ball to pass between the markings.

6. Use the magnet to remove the ball bearing.

7. Repeat 3 times and take an average.

8. Repeat steps 5-7 for different sizes of ball bearings.

Results

Area [ ]

Time [ ]

Velocity [ ]

Attempt 1

Attempt 2

Attempt 3

Average

Conclusions

Use your results to answer the following questions.

1. Was there any relationship between surface area and terminal velocity? Can you explain this result by linking to drag?………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

2. Ideally all the ball bearings would have had the same weight, explain why this would have been better?…………………………………………………………………………………………………………………………………………………………………………………………

3. Why did we not start timing the ball as soon as it entered the surface of the liquid?………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

4. Explain why the ball bearings are reaching terminal velocity inside the viscous fluid. …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

Stretch Worksheet – Newton’s 1st and 3rd Laws.

Use your MacBook and/or Textbooks to research Newton’s other laws.

· What are they?

· Why are they useful?

· When can be use them?

[Stuck: Try visiting the websites below to get you started!]

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https://www.physicsclassroom.com/class/newtlaws/Lesson-1/Newton-s-First-Law

https://www.livescience.com/46561-newton-third-law.html

http://hyperphysics.phy-astr.gsu.edu/hbase/Newt.html

Work, Power and Acceleration

Past Paper Questions

Q1.

Supermarkets use conveyer belts to move shopping at the till.

The diagram shows a carton of milk being pulled along by a horizontal conveyer belt.

The horizontal force on the carton from the belt is 1.7 N.

The carton moves a distance of 0.46 m.

(a) (i) State the equation linking work done, force and distance.

(1)

(ii) Calculate the work done moving the carton.

(2)

Work done = ........................................................... J

(iii) State how much energy is transferred to the carton.

(1)

Energy transferred = ........................................................... J

(Total for question = 4 marks)

Q2. A car pulls a caravan along a horizontal road.

(a) The car pulls the caravan with a resultant force of 170 N for a distance of 110 m.

(i) State the equation linking work done, force and distance.

(1)

(ii) Calculate the work done by the car on the caravan.

(2)

work done = ...................................... J

(iii) State how much energy is transferred to the caravan.

(1)

energy transferred = ...................................... J

(b) The caravan is removed and the car makes the return journey without it.

Without the caravan, the car has greater acceleration and uses less fuel.

Explain these changes.

(3)

.............................................................................................................................................

.............................................................................................................................................. .............................................................................................................................................

.............................................................................................................................................

............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................


Q3.

The diagram shows the driving force on a sports car as it moves along a race track.

(a) Name two forces that oppose the driving force.

.............................................................................................................................................

.............................................................................................................................................

(b) The car has a mass of 1400 kg.

The acceleration of the car is 5.5 m/s2.

(i) State the equation linking force, mass and acceleration.

(1)

(ii) Calculate the force causing this acceleration.

(2)

Force = ........................................................... N


Q4.

(a) Parachutes are used to slow down a spacecraft as it falls through the atmosphere.

Photograph G shows an Apollo spacecraft with three parachutes attached.

This spacecraft falls at a constant velocity.

(i) State the name of this constant velocity.

(1)

.............................................................................................................................................

(ii) Explain why this velocity stays at a constant value.

(3)

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

(iii) Photograph H shows an identical Apollo spacecraft. Only two of its parachutesare working.

Explain how the constant velocity reached by this spacecraft compares withthe constant velocity of the spacecraft shown in photograph G.

(2)

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

(b) Photograph I shows a Space Shuttle using a parachute when it lands on a runway.

Explain what would happen to the stopping distance of the Shuttle if this parachutedid not open.

(2)

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................


Q5.

A student investigates the motion of different falling masses by measuring the time taken for empty cupcake cases to fall from a window.

(a) The student drops one case from the window.

He repeats the experiment with two cases stuck together, then with three cases and then with four.

Name two measuring instruments that he would need for his investigation.

(2)

1 ..........................................................................................................................................

2 ..........................................................................................................................................

(b) What are the dependent and independent variables in this investigation?

(2)

dependent variable

.............................................................................................................................................

independent variable

.............................................................................................................................................

(c) State one factor that the student should keep constant in order to make this investigation valid (a fair test).

(1)

.............................................................................................................................................

(d) The student draws this table to record his results.

Add suitable headings to his table.

(2)

(e) State one way that the student can improve his investigation.

(1)

.............................................................................................................................................

.............................................................................................................................................

(f) The student notices that the cases accelerate and then fall at constant speed.

(i) The arrows in the diagrams show the size and direction of the forces acting on a case at different points in its fall.

Label the forces on the middle diagram.

(2)

(ii) Explain why the case accelerates and then falls at constant speed.

(3)

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Work, Power and Acceleration

Spec Point Notes

Work, Power and Acceleration Specification Notes

1.01use the following units: kilogram (kg), metre (m), metre/second (m/s), metre/second2 (m/s2), newton (N), second (s) and newton/kilogram (N/kg)

1.11describe the effects of forces between bodies such as changes in speed, shape or

Direction

1.12identify different types of force such as gravitational or electrostatic

Gravitational, weight, friction, electrostatic, air resistance (drag), tension (force in a spring), upthrust, lift, thurst

1.13understand how vector quantities differ from scalar quantities

· Scalars are quantities that only have magnitude (size)

· Vectors are quantities that have magnitude (size) and direction

1.14understand that force is a vector quantity

1.17know and use the relationship between unbalanced force, mass and acceleration:

force = mass × acceleration

F = m × a

1.21describe the forces acting on falling objects (and explain why falling objects reach a

terminal velocity)

4.03use the principle of conservation of energy

Energy cannot be created or destroyed it can only be transferred

4.11know and use the relationship between work done, force and distance moved in the

direction of the force:

work done = force × distance moved

W = F × d

4.12know that work done is equal to energy transferred

4.16describe power as the rate of transfer of energy or the rate of doing work

4.17use the relationship between power, work done (energy transferred) and time taken:

Power = work done/time taken

Work, Power and Acceleration – Science (Physics)41

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