A 1,200 kg car rolls down a hill with its brakes off and transmission in neutral. At one moment it is moving 5.0 m/s. A little later it is moving at 8.2 m/s. How much did its height change between the two times? Assume friction and air resistance have no effect on its motion.
(Points : 1)
1.5 m

2.2 m

4.3 m

1.9 m

Question

A 1,200 kg car rolls down a hill with its brakes off and transmission in neutral. At one moment it is moving 5.0 m/s. A little later it is moving at 8.2 m/s. How much did its height change between the two times? Assume friction and air resistance have no effect on its motion.
(Points : 1)
       1.5 m

       2.2 m

       4.3 m

       1.9 m

praxer · Answer

${8.2^2-5^2}/{2*9.8}$ $=2.15$

anonymous · Answer

That makes sense. If it comes up on the test, I will try this and let you know. Thank you for your help.

praxer · Answer

hey, it is correct see,

work = force X displacement
= mass* Acceleration due to gravity * displacement.

now potential difference = mgh= work done

=> mgh = work
=> h= displacement.