Question

Question #123a1

Answer 1

a) 30kg mass (b)mass at 75m/s (c) car rolling down hill (d) could be either

Explanation:

Kinetic energy (KE) is given by `KE=1/2mv^2`
Where `m` = mass and `v`= speed

So looking at each question:

a) both objects have the same speed (so `v^2` is the same), but different mass, `m`. The object with the higher mass (30kg) will therefore have more kinetic energy.

b) objects have the same mass (so `m` same) but with different speeds. object with higher speed (75m/s) will have more kinetic energy.

c) if the car is at rest, `v=0` so `KE=0`. Hence the car rolling down the hill has more KE (since it has some speed, `v` and thereby KE)

d) The last question is ambiguous as it doesn't tell us about the speeds. At the same speed, the heavier bike (more mass) will have higher kinetic energy. However, the smaller bike could potentially have more kinetic energy if it is travelling at faster speeds