Science Assessment ~ Topics ~ Energy: Forms, Transformation, Transfer, and Conservation ~ Item RG162002 ~ Student Performance

A child is playing with a wind-up toy car on a level surface. The child winds the car’s spring by using the wind-up key in the back of the car. A spring inside the car stores the energy the child has transferred to the car. As the spring is released, the elastic potential energy of the spring is converted into the kinetic energy (motion energy) of the car and thermal energy of the surrounding environment.

In the graphs below, Point A represents the time at which the child begins winding the toy. Point B represents the time at which the car was released and begins to travel across the floor. Point C is the time at which the car comes to a complete stop. Which of the following graphs correctly illustrates how concentrated the energy of the car is at each point?

Because energy always becomes less concentrated and cannot be made more concentrated
Because the energy of a system cannot become more or less concentrated
Because energy is concentrated as the spring is wound up and then becomes less concentrated as energy is transferred to the surrounding environment
Because energy is concentrated as the spring is wound up and then stays constant

Distribution of responses
Answer Choice		Overall	Grades			Gender		Primary Language
		n = 3305	4–5 n = 0	6–8 n = 1663	9–12 n = 1642	Male n = 1526	Female n = 1698	English n = 3006	Other n = 203
A.	Because energy always becomes less concentrated and cannot be made more concentrated	22%	N/A	24%	19%	23%	21%	21%	25%
B.	Because the energy of a system cannot become more or less concentrated	17%	N/A	18%	15%	17%	16%	16%	24%
C.	Because energy is concentrated as the spring is wound up and then becomes less concentrated as energy is transferred to the surrounding environment	49%	N/A	43%	55%	48%	50%	50%	36%
D.	Because energy is concentrated as the spring is wound up and then stays constant	13%	N/A	14%	12%	12%	14%	13%	16%

Science Assessment

Item RG162002: When a wind-up toy car is wound up and then let go, energy is concentrated as the spring is wound up and then becomes less concentrated as energy is transferred to the surrounding environment.