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Answers
Given:-
Ball is dropped on to the floor from a height of 4 m, = 4m
The ball rebounds to a height of 3 m, = 3m
The ball was in contact with the floor for 0.010s , t = 0.010s
Assumptions :-
Velocity of the ball before when dropped before striking the floor =
Velocity of the ball after striking the floor =
As the ball was in contact with the floor for 0.010 sec there must be some changes observed in the velocity of the ball, so,
Change in velocity = - (- )
Acceleration =
Case 1:-
When the ball is dropped from ,
Initial velocity, u = 0
Final velocity, v =
Acceleration, a = g = 9.8m/s²
Distance, s = = 4m
As per the 3 rd equation of motion,
v² = u² + 2as
= 0 + 2g
v² = 0 + 2 × 9.8 × 4
v² = 19.6 × 4
v² = 78.4
v =
v = 8.85 m/s
Case 2:-
When the ball rebounds after striking the floor,
Initial velocity = u
u Final velocity, v =0
Acceleration, a = g = 9.8m/s²
Distance, s = =3m
v² = u² + 2as
0 = u² - 2 × 9.8 × 3
0 = u² -19.6 × 3
0 = u² - 58.6
u² - 58.6 = 0
u = √-58.6
u = 7.67m/s
Now calculate the change in velocity,
Change in velocity = 7.67 m/s (upward) – 8.85 m/s (downward)
Δv = ( 7.67 + 8.85 ) m/s
Acceleration, a =
=
= 1652 m/s²
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