REVIEWER -3rd Quarter Science-SET A

Motion, Forces, and Energy

1: Describing and Measuring Motion

Describing Motion- an object is in MOTION if the distance between the object and another object changing; the other object we use to compare the motion is called a REFERENCE POINT.

Measuring Motion- scientist use the International System of Units

(SI) to measure using metrics a system based on the

number 10 (meters, cm, mm, km)

Speed- the distance an object travels in one unit of time

S = D/T (distance divided by time)

D = S x T (speed multiplied by time)

T = D/S (distance divided by speed)

Velocity – speed (distance divided by time)

and direction an object travels

Average Speed = total distance / total time

(total distance divided by total time)

Acceleration – rate of change in velocity; how has the object’s motion changed during a certain time frame?

1. increased speed

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REVIEWER -3rd Quarter Science-SET A

2. decreased speed

3. change in direction

A = final velocity – initial velocity

Time

2- The Nature of Force

Force is a push or pull; they have size and direction; measured in “newtons” (n)

Net force is the sum of all forces acting on an object- if NF is 0 the forces are balanced (no change in motion), if the NF is not = 0 the object’s motion will change (accelerate); the forces are unbalanced

Newton’s Laws of Motion –

1- inertia – objects resist change in their motion;

mass is a factor in inertia

2- force is the product the mass and acceleration of an object;

F= (M) (A)

3- action/reaction- when one object exerts a force on another the second object exerts a force on the first that is equal to and opposite in direction

Additional laws to know:

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REVIEWER -3rd Quarter Science-SET A

· Law of Universal Gravitation

· Law of Conservation of Momentum

Additional formulas to know

· Force = mass x acceleration

· 1 newton = 1 kg (1m/s/s)

· Momentum (p) = m(v)

Additional vocabulary to know:

· Mass and weight

· Gravity and friction

· Momentum

· Free fall and terminal velocity

· Projectile motion and satellite

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3 – Forces in Fluids

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REVIEWER -3rd Quarter Science-SET A

Pressure = Force per unit Area; measure in Pascals (Pa); P=F/A

Fluids: substance that can easily flow; gasses and liquids

Pressure decreases with elevation and increases with depth

Pascal’s Principle: an increase in pressure in a confined fluid is transmitted equally throughout the fluid; hydraulic systems are examples of this

Archimedes’ Principle: the buoyant force on an object is equal to the weight of the fluid displaced by the object

Bernoulli’s Principle: the pressure in a fluid decreases as the speed of the fluid increases

4 - Work and Machines

Work is measured in joules; it is calculated by the formula W= F(D)

Machines make work easier by either changing the direction of the force or increasing the distance over which the force is applied

Simple Machines- inclined plane, screw, pulley, wheel and axle, lever (fulcrum), wedge

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REVIEWER -3rd Quarter Science-SET A

5 – Energy and Power

Energy is the ability to do work or cause change; measured in joules

Kinetic energy is energy of motion

Potential energy is stored energy

Energy is transferred when work is done

Six forms of energy are: electrical, electromagnetic, thermal, mechanical, nuclear, and chemical

Energy Conversion: energy changes from one form to another

Law of Conservation of Energy: when energy is transferred from one object to another, no energy is created or destroyed

Power: the rate at which work is done ; Power = work/time

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