Question

a ball is thrown upwards witha speed of 19.6m. Calculate (a) the maximum height it reaches and (b) the time taken in reaching the maximum height (c) time to return its orginal position

Answer 1

The ball returns to the ground in 55 seconds. This means that the ball takes 2.52.5 seconds to attain the maximum height. Let me check if this information is correct. Applying v=u+atv=u+at, (at maximum height, the speed of the ball, v=0v=0 and a=−g=−9.8 ms−2a=−g=−9.8 ms−2) we can find that the time required to reach maximum height is 22 seconds. Hence, the given information is wrong. But, we can still solve it using another formula.

Now, applying the formula v2=u2+2asv2=u2+2as, (here, a=−g=−9.8 ms−2a=−g=−9.8 ms−2, s=hs=h , maximum height) :

02=(19.6)2+2⋅(−9.8)⋅h⟹h=19.602=(19.6)2+2⋅(−9.8)⋅h⟹h=19.6

∴∴ Maximum height attained by the