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Science Fair Collisions: Balls, Blocks and a Falling Weight

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Science Fair Collisions: Balls, Blocks and a Falling Weight

Use two science fair projects to follow energy as speeds change.

Project 1: Ball meets block

Read the passage and Table 1, then answer questions 1–6.

Two Projects, One Table

1Yusra Qasim and Teodoro Bianchi share a table at the Lakemont Middle School science fair. Both projects ask the same question: when something speeds up or slows down, where does the energy come from, and where does it go? They filmed every trial with a phone beside a meter stick and used the video to measure speeds.

2Yusra rolled a 100 g steel ball down a ramp onto a flat wooden table. At the bottom, the ball hit a 100 g wooden block that was sitting still. She started the ball from a low, a medium or a high mark on the ramp, so it reached the block at different speeds. She ran each start three times and averaged the results in Table 1. Every hit made a sharp click. After each hit, the block slid along the table and then stopped.

3In one extra trial, Yusra swapped the wooden block for a block of soft modeling clay with the same mass. The ball arrived at 1.0 m/s and stopped almost at once. The clay block slid only 1 cm, but a round dent was left in its side.

4Teodoro built a different setup. A 500 g cart sat on a level track. A string tied to the cart ran over a pulley at the end of the track to a weight hanging in the air. When Teodoro let go, the weight fell 1 m and pulled the cart along the track. The weight then landed on a foam pad, and the string went slack. After that, the cart kept rolling onto a strip of carpet, where it slowed to a stop. He tried three different hanging weights. Table 2 shows his results.

Table 1: Yusra's Ball and Block (average of 3 trials)
Start mark	Ball before hit (m/s)	Ball after hit (m/s)	Block slid (cm)
Low	0.5	0.1	2
Medium	1	0.2	8
High	1.5	0.3	18

1.

Use Table 1. Look at the medium start.

The ball's speed dropped by m/s when it hit the block.

2.

Which observation is the best evidence that energy was transferred from the ball to the block?

A. Each start mark was used for three separate trials.B. The ball rolled faster from the high mark than the low mark.C. The block began to slide just as the ball slowed down.D. The ball and the block both had a mass of 100 g.

3.

After each hit, the block slid along the table and then stopped. Where did the block's kinetic energy go?

A. It went back into the ball, which is why the ball kept rolling slowly after the hit.B. Rubbing passed it to the block and the table, warming them a tiny bit, and some became sound.C. It turned into extra mass, so the block was a little heavier after it came to a stop.D. It was used up by the sliding and stopped existing when the block came to rest.

4.

Compare the low and high starts in Table 1. Which conclusion do the data support best?

A. The faster ball lost more kinetic energy in the hit, and the block it hit slid farther.B. The faster ball kept more of its speed, so the block it hit slid a shorter distance.C. The block slid farther from the low start, since a slow ball pushes on the block for longer.D. The ball lost the same amount of speed from each mark, so the block slid the same distance.

5.

Use Table 1. When the ball's speed doubled from 0.5 m/s to 1.0 m/s, the block slid 4 times as far. Suppose Yusra builds a taller ramp so the ball hits the block at 2.0 m/s. Use the same pattern to predict the result.

The block would slide about cm.

6.

Use paragraph 3. When the ball hit the clay block at 1.0 m/s, the ball stopped and the clay block slid only 1 cm. Where did most of the ball's kinetic energy go?

A. Into pushing in and reshaping the clay, which left a dent and warmed the clay slightlyB. Into the ramp, which pushed the ball back toward the start mark after the hitC. Into the clay block's sliding, since a soft block slides farther than a hard oneD. Into the ball, which stored the energy and saved it for its next roll down the ramp

Project 2: The falling weight

Use paragraph 4 and Table 2 to answer questions 7–9. The cart's speed was measured at the moment the weight landed.

Table 2: Teodoro's Cart (500 g cart; weight falls 1 m)
Hanging weight (g)	Cart speed (m/s)	Coasted on carpet (m)
20	0.8	0.4
40	1.2	0.9
60	1.4	1.2

7.

While the weight falls, the cart speeds up from rest. Where does the energy for this increase in the cart's kinetic energy come from?

A. From the cart itself, which stores energy in its wheels before it startsB. From the foam pad, which pushes up on the weight when the weight landsC. From the level track, which pushes the cart's wheels forward as they turnD. From the falling weight, pulled down by Earth's gravity, through the string

8.

Use Table 2.

With the 60 g weight, the cart was moving m/s faster than with the 20 g weight, and it coasted m farther on the carpet.

9.

Look at the object named in each event. Sort each event by what happens to that object's kinetic energy.

Answer the judge

Use both projects to answer questions 10 and 11.

10.

A judge asks Teodoro for evidence that more energy was transferred to the cart by the 60 g weight than by the 20 g weight. Circle each piece of evidence from Table 2 that supports this.

11.

A visitor says, "In Yusra's medium trial, the ball almost stopped, so most of its energy was destroyed in the crash." Do you agree? Write a claim, give at least two pieces of evidence from Yusra's project, and explain your reasoning about what happens to energy when an object's kinetic energy changes.