Newton’s Second Law of Motion Exploration

Purpose

To explore the relationship between Force, Mass and Acceleration

Background

In this activity you will be using a video made with two carts. The two carts have identical mass and both are being pulled from the left with an equal force. The force is equal to the weight of a suspended mass. In the first set of videos, the carts are started on the right side of your screen and are simply released. In the second set of videos the carts are started on the left side of a screen and given a push in such a way that they start at the same initial velocity to the right.

As you watch the video you will be asked to make predictions of the motion. Make sure you pause the video each time you are asked a question, and respond before resuming the video to watch the motion of the carts.

Video: Newton's 2nd Law Exploration

Activity Questions

Segment 1 - Baseline

In this segment, the carts are identical, and have the same force. After watching the baseline, do you feel that the carts accelerated identically?

What might account for slight differences?

Segment 2 - Increased Mass

In this segment, the cart closer to you on the screen has an additional 1 kg of mass added to it.

Predict which cart you think will accelerate the fastest.

Observe which cart accelerated the fastest.

Segment 3 - Increased Force

In this segment, the cart closer to you on the screen has the same mass as the further cart, but now has double the force pulling it.

Predict which cart you think will accelerate the fastest.

Observe which cart accelerated the fastest.

Segment 4 - Initial Push Baseline

In this segment, the carts are identical, and have the same force and same initial push to the right. After watching the baseline, do you feel that the carts accelerated identically?

What might account for slight differences?

Segment 5 - Increased Mass

In this segment, the cart closer to you on the screen has an additional 1 kg of mass added to it. Both carts will be pushed to right with the same speed.

Predict which cart you think will slow down the fastest.

Observe which cart slowed down the fastest.

Segment 3 - Increased Force

In this segment, the cart closer to you on the screen has the same mass as the further cart, but now has double the force pulling it. Both carts will be pushed to right with the same speed.

Predict which cart you think will slow down the fastest.

Observe which cart slowed down the fastest.

Discussion Questions

1. From the videos, how could you tell the carts were accelerating and not simply moving at the same speed across the table?

2. In the second set of videos, would saying “accelerated the fastest” and “slowed down the fastest” mean the same thing? Explain.

3. Highlight the appropriate word choice in the following sentences.

• The acceleration of an object is (directly/indirectly) related to the mass of the object.
• The acceleration of an object is (directly/indirectly) related to the force on the object.
• When an unbalanced force is present in the direction of motion, it will cause the object to (speed up/slow down).
• When an unbalanced force is present in the direction opposite of motion, it will cause the object to (speed up/slow down).

4. Draw a free body diagram for one of the carts in the first video segment.

5. Would the way you diagrammed the forces be any different for any of the other video segments? Explain.

6. Are you seeing the effects of just one force or the unbalanced portion of all the forces combined? Explain.