Motion, Speed, Velocity, and Acceleration

Nadia Reese

6th grade science

Pages 86-95 in textbook

Distance

Distance – how far an object has moved. The SI unit of length is the meter (m). Longer distances are measured in

kilometers (km). Shorter distances are measured in

centimeters (cm).

Speed

Speed – the distance an object travels divided by how long it took (time).

37.5 km/hr

Velocity

Velocity– the distance an object travels divided by how long it took (time) in a certain direction.

37.5 Km/hr West

Velocity

The velocity of an object can change even if the speed remains constant.

Ex. going around a curve in cruise control

Calculating Speed/Velocity

V=d/t (distance divided by time)V = Velocity (m/s)d= distance (m) t = time (s)

Example 1

A bicycle rider travels 60.0 miles in 3 hours. What is the cyclist’s average speed?

Example 2

What is the average speed of the car that traveled a total of 300.0 miles in 6 hours?

Graphing Motion

A distance-time graph makes it possible to display the motion of an object over a period of time.

The slope of the line represents the speed. The steeper the slope, the faster the speed.

Distance-Time Graph

Distance-Time Graph

Distance-Time Graph

Distance-Time Graph

Distance-Time Graph Questions

1. What is the speed at B-C? ____________

2. How far did the car drive before it stopped the first time? _________

3. How far did the car drive the whole trip? ___________

4. How long did the whole trip take? __________

5. What is the car’s average speed? ___________

Acceleration

Acceleration is the rate of change in velocity. When the velocity of an object changes, the object accelerates.

Acceleration occurs when an object changes its speed, direction, or both.

When an object increases it velocity it is called acceleration, when an object decreases its velocity it is called deceleration.

Distance-Time Graph

Potential and Kinetic Energy

Potential Energy Kinetic Energy

Potential and Kinetic Energy

1. Create a track where all the potential energy is transferred into kinetic energy.

2. Create a track where all the potential energy is transferred into kinetic energy then back into potential energy

How are potential and kinetic energy related on a roller coaster?

Force & Motion

Thinking Questions

Can an object’s acceleration be a negative number? Why or why not?

Can an object’s acceleration be a negative number? Why or why not?

Yes. When an object slows down and the final speed is less than the initial speed, the object’s acceleration will be a negative number.

If forces occur in equal but opposite pairs, how can anything ever move?

If forces occur in equal but opposite pairs, how can anything ever move?

According to Newton’s third law, the equal and opposite forces work on different objects.

Two crates, one heavy and one light, are at rest on a waxed floor. Which crate will need a greater force to provide the same acceleration? Use the concept of inertia to explain your answer.

Two crates, one heavy and one light, are at rest on a waxed floor. Which crate will need a greater force to provide the same acceleration? Use the concept of inertia to explain your answer.

The heavy crate has more inertia, so it requires more force to make it accelerate.

Explain the role of friction in walking on a sidewalk versus walking on a sidewalk covered with ice.

Explain the role of friction in walking on a sidewalk versus walking on a sidewalk covered with ice.

Friction between your shoe and the sidewalk allows you to push against the sidewalk. Ice decreases this friction.

You sit on a rock. Your weight is a force acting on the rock. What force acts on you?

You sit on a rock. Your weight is a force acting on the rock. What force acts on you?

The rock provides an upward force that is equal to your weight since you are not moving.

How is acceleration related to change in speed?

How is acceleration related to change in speed?

Acceleration is the change in velocity divided by the time needed for the change to occur, and velocity changes when speed changes.

Balanced and Unbalanced forces http://www.engineeringinteract.org/

resources/parkworldplot/flash/concepts/balancedandun.htm

Newton’s Laws of Motion

Which groups can recall all three of Newton’s Laws? Ignite video from share drive