Answer:
Coefficient of friction.
Explanation:
The amount of friction divided by the weight of an object is equal to the coefficient of friction. It is a dimensional less number. It can be given by :

N is normal force.
= coefficient of friction

ಠ_ಠ Hey, hang on.. you might've made a discovery. Nobody has tested it so how do we know? ಠ_ಠ
Explanation:
When a constant force acts upon an object the acceleration of the object varies inversely with its mass.

or

If m₁ = 21 kg, a₁ = 3 m/s², m₂ = 9 kg
We need to find a₂
So,

So, if mass is 9 kg, its acceleration is 7 m/s².
Answer:
D. 803 lbs
Explanation:
In order to find the compressive stress on all three blocks we first need to find the normal surface area of each:
Surface Area of 1 Block = 3.5 x 3.5
Surface Area of 1 Block = 12.25
Surface Area of all 3 Blocks = A = 3 x 12.25
Area = 36.75
Now, the stress is given by the following formula:
Stress = Force/Area
Stress = 29500 lbs/36.75
Stress = 802.72 lbs
Hence, the correct option will be:
<u>D. 803 lbs</u>