OwlSheets Students

Paddleboard Science at Pine Hollow Lake

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Paddleboard Science at Pine Hollow Lake

Use a speed app's energy log and an energy inventory to argue where energy goes.

Part 1: One run across the lake

Read the passage and use Table 1 to answer questions 1–5.

The Speed App on the Paddleboard

1The summer camp at Pine Hollow Lake teaches stand-up paddleboarding to middle schoolers. On science afternoon, instructor Mr. Ronan Iwasaki strapped a waterproof phone with a speed app to the front of his board. The app recorded the board's speed. It also used the total mass of the board, rider and gear, 80 kg, to show their kinetic energy in joules. Camper Delfina Kask kept the log from the dock while the rest of her group watched and called out what they saw.

2Mr. Iwasaki started from a standstill and paddled hard for 8 strokes. Then he lifted his paddle out of the water and glided across open water. Next he glided into a patch of lily pads. The pads bent and slid aside as the board pushed through, and they kept rocking for a few seconds after he passed. As he drifted out of the patch, a gust of wind blew from behind him while he held his paddle up out of the water.

3Last, he glided slowly into the camp's floating swim platform, which has a mass of 160 kg, a rubber bumper along its edge and a loose rope tying it to an anchor. When the board hit the bumper, the board stopped. The bumper squashed in and sprang back, the campers heard a dull thud and small waves spread out from the platform. The platform drifted away at about 0.5 m/s until its rope pulled tight. Delfina used the app's numbers to make an energy inventory of the bump (the bar graph in Part 2).

Table 1: Delfina's Log (board, rider and gear: 80 kg)
Stage	What happened	Speed before (m/s)	Speed after (m/s)	KE before (J)	KE after (J)
1	Paddled 8 strokes from a standstill	0	2	0	160
2	Glided in open water for 10 s	2	1.5	160	90
3	Glided through lily pads for 5 s	1.5	0.5	90	10
4	Gust from behind for 6 s, paddle up	0.5	1	10	40
5	Glided into the platform's bumper	1	0	40	0

KE means kinetic energy, the energy an object has because it is moving.

1.

Use Table 1. Circle each stage in which the kinetic energy of the board and rider went down, so energy was transferred from them to something else, such as the water, the plants or the platform.

2.

Use Table 1. Look at Stage 1.

During the 8 strokes, the kinetic energy of the board and rider rose by an average of J per stroke.

3.

Use Table 1. Find how much kinetic energy the board and rider lost in each glide.

In the 10 s glide in open water, they lost J. In the 5 s glide through the lily pads, they lost J.

4.

Use paragraph 2 and your answers to question 3. Why did the board lose more kinetic energy in the lily pads, in half the time?

A. The wet pads stuck to the board and added mass, and the extra mass used up its energy.B. The board pushed the pads aside and set them rocking, so energy left the board faster.C. The cool pads took thermal energy from the rider's feet, which slowed the board down.D. The board was moving faster when it entered the pads than when the open-water glide began.

5.

Which observation is the best evidence that the gust of wind in Stage 4 transferred energy to the board and rider?

A. The board was moving at 0.5 m/s, slower than at any other time in the log.B. The gust lasted 6 s, about as long as the glide through the lily pads.C. The board sped up from 0.5 to 1.0 m/s while the paddle was out of the water.D. The board, rider and gear still had a mass of 80 kg after the gust.

Part 2: The energy inventory of the bump

Use the bar graph, Table 1 and paragraph 3 to answer questions 6–10.

6.

Use the bar graph. Before the bump, the board and the platform had 40 J of kinetic energy in all.

Right after the bump, J of that 40 J was no longer kinetic energy of the board or the platform.

7.

Use paragraph 3. Circle each observation that is evidence that some of the board's energy went to things other than the platform's motion.

8.

Suppose Mr. Iwasaki glides into the bumper at 2.0 m/s instead of 1.0 m/s. Use Table 1 to find the kinetic energy at 2.0 m/s. Which prediction fits the data best?

A. The board would bring 160 J, four times as much, so more energy would go to the platform.B. The board would bring the same 40 J, since the mass of 80 kg has not changed.C. The board would bring 80 J, twice as much, so the platform would move a little faster.D. The board would bring 160 J, but a faster bump is shorter, so less would go to the platform.

9.

Match each event to where the energy for the change in kinetic energy came from or went.

10.

Delfina claims, "In the bump, energy was transferred from the board to the platform and to its surroundings." Support or reject her claim. Use evidence from the bar graph, Table 1 and paragraph 3, and explain your reasoning about what a change in kinetic energy shows.