A boy throws a ball vertically up. It returns to the ground after 5 seconds. Find
(a) the maximum height reached by the ball.
(b) the velocity with which the ball is thrown up.

31.25 m

25m/sec

Explanation:

Given :-

Time = 5sec

V = 0 (in going up)

U = 0 (in comming down)

Find :-

H and U by which it is thrown up

Since the total time is 5 sec ,therefore half time will be taken to go up and another half will be taken to go down .

We know that ,

V = U + gt

0 = U - 10*2.5

U = 25 m/sec

Also,

V² = U² +2gs

0 = 625 - 20s

s = 625/20 = 31.25 m

3. dark matter

empty space could also be a simple vacuum

electrical potential energy =0.072 j

explanation:

electrical potential energy is given by

u= q δv

q= charge=6 c

δv= potential difference and is given by

δv= e d

e= electric field

d= distance=5 mm=0.005 m

δv=2.4 (0.005)=0.012 v

now electric potential energy= u= q δv

u=6 (0.012)

u=0.072 j