Hi there!
We know that:
U (Potential energy) = mgh
We are given the potential energy, so we can rearrange to solve for h (height):
U/mg = h
g = 9.81 m/s²
m = 30 g ⇒ 0.03 kg
0.062/(0.03 · 9.81) = 0.211 m
Answer:
a) The answer is 11,7m
b) The time it takes to fall will be shorter
Explanation:
We will use the next semi-parabolic movement equations
Where g(gravity acceleration)=9,81m/s^2
Also Xi, Hi and Viy are zero, as the stones Billy-Jones is kicking stay still before he moves them, so we take that point as the reference point
The first we must do is to find how much time the stones take to fall, this way:
Then t=1,54s
After that we need to replace t to find H, this way
Then H=11,7m
b) The stones will fall faster as the stones will be kicked harder, it will cause the stones move faster, it means, more horizontal velocity. In order to see it better we could assume the actual velocity is two times more than it is, so it will give us half of the time, this way:
Then, t=0,77
Usually the unit of measurement of velocity is meters per second or m/s
(a) 1200 rad/s
The angular acceleration of the rotor is given by:

where we have
is the angular acceleration (negative since the rotor is slowing down)
is the final angular speed
is the initial angular speed
t = 10.0 s is the time interval
Solving for
, we find the final angular speed after 10.0 s:

(b) 25 s
We can calculate the time needed for the rotor to come to rest, by using again the same formula:

If we re-arrange it for t, we get:

where here we have
is the initial angular speed
is the final angular speed
is the angular acceleration
Solving the equation,
