Question

A body is thrown horizontally from the top of
a tower. It reaches the ground after 4s at an
angle 45° to the ground. The velocity of
projection is
1) 9.8 ms-1
2) 19.6 ms-1
3) 29.4 ms-1
4) 39.2 ms-1

Answer 1

Answer:

The only force acting in the vertical direction is the downward force ie. the force of gravity. As the body was thrown horizontally ,hence the initial velocity of the body in downward direction is zero . So ,the time of downward motion can be found using equation:

S=ut+1/2at²

Where u=0 ,a=g~10 and S=height of the tower =5m

So ,time of the downward motion is equal to 1 second. The given range of the body is 10m,as no force is acting in the horizontal direction . Hence ,the velocity of the body in the horizontal direction will not change ie. Initial velocity in x- direction =final velocity in x-direction.

Distance travelled= velocity ×time of downward motion .

Hence , the initial velocity is equal to 10m/s in horizontal direction.