Question

an object is thrown vertically upward and pases through same point after 2 sec and 10 sec respectively, the time at which its velcoity becomes zero is

Answer 1

Answer:

52

Explanation:

Here the time 5 sec is for the body to rise from 10.2 m elevation to the maximum height and another 5 sec is for fall back to 10.2 m elevation.

Since at highest point the velocity of the body is zero, so the velocity at 10.2 m height is vh=gt=10(5)=50m/s   (using v=u+at here v=0,u=vh,a=−g)

Using conservation of energy, mgh=21m[v02−vh2]

or v02=2gh+502=2(10)(10.2)+502

or v0=52m/s