- At time t = 0, a small ball is projected vertically upwards from a point A which is 24.5 m above the ground. The ball first comes to instantaneous rest at the point B, where AB = 19.6 m and first hits the ground at time t = T seconds. = The ball is modelled as a particle moving freely under gravity. (a) Find the value of T.

5 sec

Explanation:

t1 is time moving upwards and t2 is time moving downwards.

For v=0 when the ball is highest

s= -1/2(-g)(t1)^2

where s=AB=19.6m and g=9.8m/s^2

Solving t1=2 sec

The height at t1 is 44.1m

and the ball would move through gravity with zero initial velocity.

s= 1/2g(t2)^2

where s=44.1m

Solving t2=3sec

Total time consumed is T= t1+t2= 5sec

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.