Answer:

Explanation:
From the law of conservation of energy
Energy lost by the spring, W=Kinetic energy gained, KE+Potential energy gained, PE+Work done by friction, Fr



The required distance from A to B is 
The answer is c. the force of his swing
At the time of the impact, there is a collision between two bodies moving in opposite directions.
The force exerted on the ball causes the change of velocity.
Answer:
I would say the answer is A... but I'm not so sure ....
X=1/2 at^2
3.1=1/2 a *0.64
a=9.68
v=at
v=0.8*9.6875=7.75
Answer:height above ground at which projectile have velocity
0.5v is (0.0375v^2)
Explanation:
Using Vf = Vi - gt
Where Vf is final velocity
Vi is initial velocity
g is the acceleration due to gravity
t is the time taken
So, 0.5v = v - gt
t = 0.05v
Therefore height h = vt - 0.5gt^2
Subtitute t
h = 0.05v^2 - 0.0125v^2
h = 0.0375v^2