Question

If two bodies have masses in the ratio 1:8 ,have their speed in the ratio 4:5 ,find the ratio of their KE.
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Answer 1

Answer:

4:25

Explanation:

Let the masses be m and 8m.

Let the speeds be 4v and 5v.

KE = 1/2mv^2

KE' = 1/2*m*(4v)^2 = 1/2*m*16v^2 = 8mv^2

KE'' = 1/2*4m*(5v)^2 = 2m* 25v^2 = 50mv^2

KE'/KE'' = 8mv^2/50mv^2 = 4/25 = 4:25