Answer
Maximum speed at 75 m radius will be 22.625 m /sec
Explanation:
We have given radius of the curve r = 150 m
Maximum speed 
Coefficient of friction 
Now new radius r = 75 m
So maximum speed at new radius 
All sources of energy on the planet (excluding nuclear reactions) are ultimately attributable to the sun. 'Fossil fuels' are derived from what once were living organisms, and all sources of food begin with primary producers (plants and algae which utilize photosynthesis).
One possible unit is liter, which is a basic unit in metric system. 1 liter=10 cm^3, or 0.001 m^3, so we also know that other possible units include cubic centimeters or cubic meters, which are derived units, since they are derived from basic unit, meter, representing the length, breadth, and height of the cuboid.
You can do this two ways:
1). Whatever kinetic energy the rolling ball has is the amount
of energy you have to absorb in order to stop it.
2). Whatever momentum the rolling ball has is the amount of
momentum you have to provide in the other direction to cancel it.
Since you asked about force and time, we sense 'impulse' in the
air, and we know that impulse is exactly a change in momentum.
So let's use #2 and talk about momentum and impulse.
Impulse = (force) x (time)
Momentum of a moving object is (mass) x (speed) .
-- Momentum of the first ball: (8 kg) x (0.2 m/s) = 1.6 kg-m/s
Impulse required to stop it = 1.6 kg-m/s
(force) x (10 sec) = 1.6
Force required = 1.6 / 10 = 0.16 Newton .
-- Momentum of the second ball: (4 kg) x (1 m/s) = 4 kg-m/s
Impulse required to stop it = 4 kg-m/s
(force) x (10 sec) = 4
Force required = 4 / 10 = 0.4 Newton .
You need more force o stop the second ball. Although its mass
is only 1/2 the mass of the 8kg ball, it's moving 5 times as fast,
and has 2.5 times the momentum of the bigger ball.
So you need 2.5 times as much impulse to stop it.
If you're going to push on each ball for the same length of time,
then you need to push 2.5 times as hard on the smaller ball in
order to stop it.
