Answer:
c. 3/2 mg
Explanation:
Given that the acceleration of an elevator is 1/2 g upward.
The reading on the scale of the elevator is the net external force acting on the elevator.
Let the force F acting on the elevator as shown,
By using Newton's 2nd law, 
where,
is the net force acting on the elevator.
m is the mass of the elevator,
a is the acceleration of the elevator, as given a=1/2 g upward.
So, 

So, the reading on the scale in the elevator is
.
Hence, option (c) is correct.
<h3>
Answer:</h3>
375 N
<h3>
Explanation:</h3>
Topic tested: Newton's Law of motion
The question is testing on the application of Newton's second Law of motion.
We are given;
- Mass of the football = 5 Kg
- Initial velocity of the football, Vf = 15 m/s
- Time taken to bring the ball to rest = 0.2 s
- Final velocity, Vo = 0 m/s ( since the ball went to rest)
We are required to determine the force exerted to bring it to rest.
- According to the Newton's second law of motion the resultant force and rate of change in momentum are directly proportion.

Thus;


Force = 375 N
Hence, the force exerted on the ball by the receiver was 375 N
Sitting. Because its no move at all