Energy at the Batting Cage

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Energy at the Batting Cage

Use pitching machine and catch data to track energy into and out of a softball.

Part 1: The pitching machine

Read the passage and the machine table. Use them to answer questions 1–5.

Data Day at the Cage

1Harper Nakashima plays second base on her middle school softball team. Before the season, Coach Delroy Banks set up a "data day" in the batting cage. A pitching machine with two rubber wheels, each spun by an electric motor, stood at one end of the cage. When a ball is fed between the spinning wheels, they grip it and fling it toward home plate. A dial sets the machine to low, medium or high.

2Coach Banks used a radar gun to measure the ball's speed as it left the machine and again as it reached the plate. A sensor on the machine counted how fast the wheels were spinning, in rotations per minute (rpm). Each time a ball shot out, the wheels slowed down for a moment, and then the motors brought them back up to speed in about one second. The coach's tablet app used the mass of the ball, 0.19 kg, and its speed to calculate its kinetic energy in joules (J).

3Next, the team tested what happens when the moving ball is stopped. With the machine on medium, Harper's teammate Rosa caught 30 pitches in her catcher's mitt, and each catch made a loud pop. Afterward, an infrared thermometer showed that the pocket of the mitt was 2 °C warmer than it had been at the start. Then Rosa stepped aside, and balls flew into the back net, which bulged backward about 40 cm and swung for a few seconds. A ball that hit a thick foam crash pad bounced back slowly, and the foam showed a dent that filled back in over a minute.

4Last, Harper took her turn at bat. Her bat slowed down at the moment it struck the ball, and the ball flew back toward the machine faster than it had arrived.

Pitching Machine Tests (average of 5 pitches)
Setting	Speed leaving (m/s)	Kinetic energy (J)	Wheel slowdown (rpm)
Low	15	21	40
Medium	20	38	70
High	25	59	110

1.

A softball sits still before it is fed into the machine, then leaves at 20 m/s. Where did the energy for its increase in kinetic energy come from?

A. The ball made new energy as it was squeezed by the rubber wheels.B. The ball had stored the energy inside it since it was made.C. The spinning wheels, kept turning by motors that use electricityD. The air in the cage, which pushed the ball out of the machine

2.

How many more joules of kinetic energy did a ball have on high than on low? J

3.

Which observation is the best evidence that the wheels transferred energy to each ball?

A. The wheels slowed more when the ball left with more energy.B. Each ball had the same mass of 0.19 kg on every setting.C. The machine was set to low, medium or high with a front dial.D. The radar gun measured each ball's speed again at the plate.

4.

On medium, a ball left the machine with 38 J of kinetic energy. When it reached the plate, the radar read 19 m/s, and the app showed 34 J.

How much kinetic energy did the ball lose on its way to the plate? J

5.

Where did most of those joules go while the ball was in flight?

A. They went to the air the ball pushed out of its way.B. They stayed in the ball as extra mass it picked up.C. They were destroyed by gravity as the ball flew.D. They went back into the machine's spinning wheels.

Part 2: Catching and hitting

Use the catch table and the passage to answer questions 6–10.

What Happened at the Plate (machine on medium)
Event	Speed before (m/s)	Speed after (m/s)	Energy after (J)
Catcher's mitt	19	0	0
Back net	19	0	0
Foam crash pad	19	4	1.5
Harper's bat	19	28	74

6.

Circle each event in which the softball's kinetic energy decreased.

7.

Which observation is the best evidence that the ball's energy was transferred to the back net?

A. The ball dropped to the ground below the net after it stopped.B. The machine was set to medium while balls flew into the net.C. The ball's speed was 19 m/s just before it reached the net.D. The net bulged backward about 40 cm and swung for a few seconds.

8.

A ball reaching the plate at 19 m/s has 34 J of kinetic energy. Use the table.

How much kinetic energy did the ball lose when it bounced off the foam crash pad? J

9.

After 30 catches, the pocket of Rosa's mitt was 2 °C warmer. What is the best conclusion?

A. The mitt gave its cold to the balls, so each ball slowed down to a stop.B. Part of each ball's kinetic energy went into the mitt as thermal energy.C. The balls warmed up in flight and then passed that warmth to the mitt.D. Rosa's hand made the mitt warmer, so the catches had little to do with it.

10.

Harper's friend says, "After the bat hit, the ball had more energy than the machine gave it, so the extra energy came from nowhere." Do you agree? Write a claim, give evidence from the passage and the tables, and explain your reasoning about energy transfer.