Answer:
Useful Output = 35 J
Explanation:
The useful energy output of the car must be equal to the difference between the total input energy supplied to the car and the energy wasted by the car:
Useful Output = Total Input - Waste
where,
Total Input = 120 J
Waste = 85 J
Therefore,
Useful Output = 120 J - 85 J
<u>Useful Output = 35 J</u>
Answer:

Explanation:
If the collision is elastic and exactly head-on, then we can use the law of momentum conservation for the motion of the 2 balls
Before the collision

After the collision

So using the law of momentum conservation


We can solve for the speed of ball 1 post collision in terms of others:

Their kinetic energy is also conserved before and after collision


From here we can plug in 






Answer:
-1.43 m/s relative to the shore
Explanation:
Total momentum must be conserved before and after the run. Since they were both stationary before, their total speed, and momentum, is 0, so is the total momentum after the run off:
where
are the mass of the swimmer and raft, respectively.
are the velocities of the swimmer and the raft after the run, respectively. We can solve for
So the recoil velocity that the raft would have is -1.43 m/s after the swimmer runs off, relative to the shore
I am not completely sure, but I believe that it depends on the total mass of the Protons and Neutrons