HPQ:Physics:KineticEnergy:KS4:Sergio Fabbri

A black 1600-kg car is travelling at a constant speed of 40 km/h. Another white 800-kg car is travelling at a constant speed of 80 km/h. What can we say about their kinetic energies KE? (No calculator.)

A. KE (black) = KE (white)

B. KE (black) = 4 · KE (white)

C. KE (black) = 0.5 · KE (white)

D. KE (black) = 2 · KE (white)

E. KE (black) = KE (white) / 4

Ans. D

CONTEXT Age 14, the students are analysing the kinetic energy characteristics. Until the previous year they lived in the world of the direct proportionality dictatorship. This HPQ is aimed to control if they digested what the squared speed in the KE formula means. I used some (in a sense, useless) data so that they can find the correct solution via calculation (the abstract reasoning is a bit complicated yet - at least for the vast majority of my students).


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