B) 48.0 m/s
We can actually start to solve the problem from B for simplicity.
The motion of the rock is a uniformly accelerated motion (free fall), so we can find the final speed using the following suvat equation
where
is the final velocity
is the initial velocity (positive since we take downward as positive direction)
is the acceleration of gravity
s = 110 m is the vertical displacement
Solving for v, we find the final velocity (and so, the speed of the rock at impact):
A) 3.67 s
Now we can find the time of flight of the rock by using the following suvat equation
where
is the final velocity at the moment of impact
is the initial velocity
is the acceleration of gravity
t is the time it takes for the rock to reach the ground
And solving for t, we find
Answer:
10 m/s
Explanation:
Use the kinetic energy formula:
KE=(1/2)mv^2
I always remember it as Kevin is half-mad, and very square.
25J = (1/2)*0.5kg*(v^2)
50J = 0.5kg*(v^2)
100J = v^2
v = 10 m/s
Check it:
KE = (1/2)*0.5*(10^2)
KE = 25J
yep, it's right!
Added potential energy = (mass) x (gravity) x (height)
or
Added potential energy = (weight) x (added height)
If you need to lift a 15N box 3m straight up, you have to increase its potential energy by (15 N) x (3 m) = 45 Joules .
Where is that added potential energy supposed to come from ? You could use an electric winch, a steam engine, a gasoline-powered motor, thousands of hamsters running on little treadmills that are are connected to the main pulley somehow, or your own arm muscles. But howEVER you do it, you have to provide <em>45 Joules</em> of WORK in order to increase the potential energy of the box by just that much.
Thus, area is the product of two lengths and so has dimension L2, or length squared.
