The answer to the problem b.
Answer:
The the average magnitude of the force exerted on the ball by the floor
N
Explanation:
Given:
Mass of ball
kg
Initial speed 
Rebound speed 
Contact time interval
sec
For finding the average magnitude of the force on the ball by the floor is given by,

Here 


N
Therefore, the the average magnitude of the force exerted on the ball by the floor
N
I believe the answer is C: For objects at extremely fast speeds.
Hope this helps!
Answer:
Resistance of gold wire, 
Explanation:
In this question we have given
Density of gold, 
resistivity of gold, 
Length of wire, 
Temperature, 
We know that relation between volume and density is given as

Therefore, volume occupied by one gram gold is given as,
.........(1)
We Know that Volume of gold wire which is cylindrical in shape is given by following formula
......(2)
Here,
...........(3)
here A is the cross sectional area of cylendrical gold wire
From equation 2 and 3
we got
...............(4)
on comparing equation 1 and equation 4, we got,



we know that resistance and resistivity are related by following formula,
................(5)
Put values of resistivity, A and L in equation 5, we got


Therefore resistance of gold wire, 