Answer:
Explanation:
Given
Each student exert a force of 
Let mass of car be m
there are 18 students who lifts the car
Total force by 18 students 
therefore weight of car 
mass of car 

(b)
Answer:
Explanation:
To stop a ball with high momentum in a small-time imparts a high amount of impact on hands. This is the reason for the stinging of hands.
The momentum of the ball is due to the mass and velocity. To prevent stinging in the hand one needs to lower his hands to increase the time of contact. In this way, the momentum transfer to the hands will be lesser.
Answer:
Add a picture please..God bless you.
Explanation: