Answer:
The work done by friction was 
Explanation:
Given that,
Mass of car = 1000 kg
Initial speed of car =108 km/h =30 m/s
When the car is stop by brakes.
Then, final speed of car will be zero.
We need to calculate the work done by friction
Using formula of work done



Put the value of m and v



Hence, The work done by friction was 
Answer:
100N
Explanation:
Newton's third law states that whenever an object exerts a force on a second object, it exerts a force of equal magnitude and direction but in the opposite direction on the first. It is often stated as follows: Each action always opposes an equal but opposite reaction.
The subject 1 of 100kg is making a force F, to move an object from 50Kg to 2m / s ^ 2. This Force the object of 50Kg will reflect it in the opposite direction by Newton's third law.
Once the parameter of the force that both are experiencing is clarified, Newton's second law is applied to their respective calculation.

That is the force the boy exert on the man during the shove.
Answer:
x = 0.974 L
Explanation:
given,
length of inclination of log = 30°
mass of log = 200 Kg
rock is located at = 0.6 L
L is the length of the log
mass of engineer = 53.5 Kg
let x be the distance from left at which log is horizontal.
For log to be horizontal system should be in equilibrium
∑ M = 0
mass of the log will be concentrated at the center
distance of rock from CM of log = 0.1 L
now,
∑ M = 0



x = 0.974 L
hence, distance of the engineer from the left side is equal to x = 0.974 L