Science Assessment ~ Topics ~ Energy: Forms, Transformation, Transfer, and Conservation ~ Item RG002003 ~ Student Performance

A cart full of apples is rolling along a road. As it rolls, many of the apples fall out of the cart. As the apples fall out, the total mass of the cart and apples decreases by half, but the speed of the cart does not change. What happens to the kinetic energy (motion energy) of the cart as the apples fall out?

The kinetic energy of the cart decreases by half because the amount of kinetic energy an object has is directly proportional to the mass of the object.
The kinetic energy of the cart is one fourth of what it was because the amount of kinetic energy an object has is directly proportional to the square of the mass of the object.
The kinetic energy of the cart doubles because the amount of kinetic energy an object has is inversely proportional to the mass of the object.
Even though the mass of the cart and apples changes, the kinetic energy of the cart stays the same because the amount of kinetic energy an object has is not related to the mass of the object.

Distribution of responses
Answer Choice	Overall	Grades			Gender		Primary Language
	n = 1136	4–5 n = 0	6–8 n = 622	9–12 n = 514	Male n = 559	Female n = 554	English n = 997	Other n = 108
A.	28%	N/A	29%	28%	27%	30%	28%	28%
B.	22%	N/A	21%	23%	21%	22%	21%	29%
C.	24%	N/A	23%	24%	23%	24%	23%	28%
D.	26%	N/A	27%	26%	28%	25%	27%	16%

Science Assessment

Item RG002003: Kinetic energy is proportional to mass, so when a moving object has its mass decreased by half the kinetic energy of that object decreases by half.