Where’s the question page at??
Well,
A control in an experiment would basically be the "normal" version of your test subjects.
In a drug testing experiment with people, the control group would be the people who don't take the drug.
In an experiment on the effects of salt on potatoes, the control group would be a potato without salt on it.
So in an experiment to measure the effects of gas additives on fuel, the control would be fuel without additives.
Answer:
Part a)

Part b)
Direction = upwards
Explanation:
When ball is dropped from height h = 4.0 m
then the speed of the ball just before it will strike the ground is given as



Now ball will rebound to height h = 2.00 m
so the velocity of ball just after it will rebound is given as



Part a)
Average acceleration is given as



Part B)
As we know that ball rebounds upwards after collision while before collision it is moving downwards
So the direction of the acceleration is vertically upwards
Answer:
F = 7,916,955.0N
Explanation:
According to newtons second law
Force = mass * acceleration
Given
mass = 52.0kg
distance S = 22.0m
time t = 17.0 ms = 0.017s
We need to get the acceleration first using the formula;
S = ut+ 1/2at²
22 = 0 + 1/2 a(0.017²)
22 = 0.0001445a
a = 22/0.0001445
a = 152,249.13m/s²
The magnitude of the average force exerted will be;
F = ma
F = 52 * 152,249.13
F = 7,916,955.0N