Answer:
Therefore, the situation in which both the instantaneous velocity and acceleration become zero, is the situation when the ball reaches the highest point of its motion.
Explanation:
When a ball is thrown upward under the free fall action of gravity, it starts to loose its Kinetic Energy as it moves upward. As the ball moves in upward direction, its kinetic energy gradually converts into its potential energy. As a result the speed of the ball starts to decrease as it moves up. Therefore, at the highest point during its motion, the velocity of ball becomes zero and it stops at the highest point for a moment, and then it starts to fall back down, under the influence of gravitational force.
Therefore, the situation in which both the instantaneous velocity and acceleration become zero, is the situation <u>when the ball reaches the highest point of its motion.</u>

for a solid cylinder:

for a hollow cylinder:

I will look at the case of a hollow cylinder:

That is as far as i get.
Answer:
Of course harder
Explanation:
Just imagone the floor is wet and you walk on it, do u feel it hard or easy to walk? :D
Answer:
part (a) 
part (b) N = 79.61 rev
part (c) 
Explanation:
Given,
- Initial speed of the wheel =

- total time taken = t = 20.0 sec
part (a)
Let
be the angular acceleration of the wheel.
Wheel is finally at the rest. Hence the final angular speed of the wheel is 0.

part (b)
Let
be the total angular displacement of the wheel from initial position till the rest.

We know, 1 revolution =
rad
Let N be the number of revolution covered by the wheel.

Hence the 79.61 revolution is covered by the wheel in the 20 sec.
part (c)
Given,
- Mass of the pole = m = 4 kg
- Length of the pole = L = 2.5 m
- Angle of the pole with the horizontal axis =

Now the center of mass of the pole = 
Weight component of the pole perpendicular to the center of mass = 

The volume of a cylinder is PI*R^2H where PI is a regular, R is the radius and H the height. Consequently, the quantity of the iron rod could be (3.141)*((2.05/2)^2)*(ninety four.Three) = 311.2 cm^three. The density of Iron is 7.874 gm/cm^3, so the whole weight would be 2449 grams, or about 2.5 kilograms.