Home
Class 12
PHYSICS
A man who is running has half the kineti...

A man who is running has half the kinetic energy of a boy of half his mass. The man speeds up by 1 `ms^(-1)` and then has the same kinetic energy as the boy. The original speed of the boy was:

A

`2 m//s`

B

`9.6 m//s`

C

`4.8 m//s`

D

`7.2 m//s`

Text Solution

Verified by Experts

The correct Answer is:
C
If original speed of boy is then
`1/2 M v^2 = 1/2[1/2 M/2 v_0^2] " "….(i)`
Also, `1/2 M (v + 1)^2 = 1/2 M/2 v_0^2 " "…..(ii)`
From Eqs. (i) and (ii) `" "((v + 1)/v)^2 = 2 implies v = 1/(sqrt(2) - 1) , " " v = sqrt(2) + 1 = 2.41 m//s`
From equation (i), `v_(0) = 2 v = 4.8 m//s` .
Promotional Banner

Similar Questions

Explore conceptually related problems

A running man has half the KE that a body of half his mass has. The man speeds up by 1.0ms^(-1) and then has the same energy as the boy. What were the original speeds of the man and the boy?

A running man has the same kinetic energy as that of a boy of half his mass. The man speed up by 2 ms^(-1) and the body changes his speed by x ms^(-1) so that the kinetic energies of the boy and the man are again equal. Then x in ms^(-1) is

If the speed of a vehicle is increased by 1 ms^(-1) , its kinetic energy is doubled , then original speed of the vehicle is