Question 18: a
question 19: b
question 20: c
To solve this problem we will apply the concept related to the kinetic energy theorem. Said theorem states that the work done by the net force (sum of all forces) applied to a particle is equal to the change experienced by the kinetic energy of that particle. This is:


Here,
m = mass
v = Velocity
Our values are given as,


Replacing,


Therefore the mechanical energy lost due to friction acting on the runner is 907J
Answer:
Average speed of the car A = 70 miles per hour
Average speed of the car B = 60 miles per hour
Explanation:
Average speed of the car A is
(Equation A) and Average speed of the car B is
(Equation B), where
and
are the distances and
and
are the times at which are travelling the cars A and B respectively.
We have to convert the time to the correct units:
1 hour and 36 minutes = 96 minutes

From the diagram (Please see the attachment), we can see that at the time they meet, we have:
(Equation C)
(Equation D)
From Equation A and C, we have:

208-x+16 = x
208 + 16 = 2x

x = 112 miles
Replacing x in Equation A:


Replacing x in Equation B:


