Question

An object A has half the mass and twice the velocity of object B. How are the kinetic energies of A and B related?

A. The kinetic energy of B is 4 times that of A.
B. The kinetic energy of B is twice that of A.
C. The kinetic energy of A is the same as that of B.
D. The kinetic energy of A is twice that of B.

I have no clue as to what the answer is

Answer 1

I find that when these problems start that 1/2 of this and twice something of that the easy way to keep things straight is to simply assign arbitrary numbers to one of the objects. For example, say A has a mass of 2 kg and a velocity of 2 m/s.
Usinsg that as a starting point calculate mass of B and velocity of B.

Then calculate KE of A and KE of B the choose the answer choice that matches. If you don't like to start with 2 and 2 you're welcome to choose different numbers. It makes no difference what numbers you choose so make them easy to use.
I'll be glad to check your answer but you can't miss with this.

Answer 2

I but in different numbers and it seems that b and d are answers

Answer 3

You're not interpreting the choices correctly.
What do you have for KE of A and KE of B and what numbers did you use to get KE?

Answer 4

The answer is D.) The kinetic energy of A is twice that of B. I promise