Answer:

Explanation:
Given that,
Initial angular velocity, 
Acceleration of the wheel, 
Rotation, 
Let t is the time. Using second equation of kinematics can be calculated using time.

Let
is the final angular velocity and a is the radial component of acceleration.

Radial component of acceleration,

So, the required acceleration on the edge of the wheel is
.
Answer:
Mass of the disk will be 2.976 kg
Explanation:
We have given force F = 45 N
Radius of the disk r = 0.12 m
Angular acceleration 
We know that torque 
And 
So
, here I is moment of inertia
So 

We know that moment of inertia 
So 
m = 2.976 kg
The added weight of the sand puts more downward pressure on the wheels contacting the rails, which would cause the trains speed to decrease.
As the ball is moving in air as well as we have to neglect the friction force on it
So we can say that ball is having only one force on it that is gravitational force
So the force on the ball must have to be represented by gravitational force and that must be vertically downwards
So the correct FBD will contain only one force and that force must be vertically downwards
So here correct answer must be
<em>Diagram A shows a box with a downward arrow. </em>