Question

A ball of mass 200
gram is thrown vertically upward
with a velocity of 100 m per second. Calculate how high
will it rises given g= 10 m per second​

Answer 1

Explanation:

Given Initial velocity of ball, u=49 m/s

Let the maximum height reached and time taken to reach that height be H and t respectively.

Assumption: g=9.8 m/s

2

holds true (maximum height reached is small compared to the radius of earth)

Velocity of the ball at maximum height is zero, v=0

v

2

−u

2

=2aH

0−(49)

2

=2×(−9.8)×H

⟹H=122.5 m

v=u+at

0=49−9.8t

⟹t=5 s

∴ Total time taken by ball to return to the surface, T=2t=10 s

Answer 2

Since the ball is thrown upward so as per equation “v=u+at” by keeping value of v=0 ,u=30 and a=g(acceleration due to earth' gravity) we get to know that in approximately 3s (takeg=10m/s^2) the ball will stop and start moving downwards so then after 2 seconds its velocity 'v' will be v=u+at here u=0 so v will be 20m/s.Hence kinetic energy will be after 5s of throwing ball upwards 0.5*m*v^2 so it will be 0.2*20*20*0.5=40 joules(by taking g=10m/s^2)