Questions 35–38 refer to a large truck which breaks down out on the road and rec

Question

Questions 35–38 refer to a large truck which breaks down out on the road and receives a push back to town by a small compact car.

Pick one of the choices A through J below which correctly describes the forces between the car and the truck for each of the descriptions (35–38).

35. The car is pushing on the truck, but not hard enough to make the truck move.
B  

36. The car, still pushing the truck, is speeding up to get to cruising speed.
A  

37. The car, still pushing the truck, is at cruising speed and continues to travel at the same speed.
C  

38. The car, still pushing the truck, is at cruising speed when the truck puts on its brakes and causes the car to slow down.
B  

A.     The force of the car pushing against the truck is equal to that of the truck pushing back against the car. B.     The force of the car pushing against the truck is less than that of the truck pushing back against the car. C.     The force of the car pushing against the truck is greater than that of the truck pushing back against the car. D.    
The car's engine is running so it applies a force as it pushes against the truck, but the truck's engine isn't running so it can't push back with a force against the car. E.    
Neither the car nor the truck exert any force on each other. The truck is pushed forward simply because it is in the way of the car. J.     None of these descriptions are correct.

Explanation / Answer

(1) To move the truck,we need to overcome static friction which is slef adjustable force means if the static friction is 10 N and we apply any force less than 10 N then it will also apply the same amount of force back to us.
But if we apply force more than 10 N then it will apply only 10 N to us.
That's why if car is pushing on the truck but unable to move it that means the applied force is less than static friction. Hence static friction will balnced our force.
hence the correct option will be A.
(2) According to newton third law, every action is having equal and opposite reaction.
hence correct option is A.
And D option is also correct.
(3) Here the net force must be zero to have constant speed. therefore force must be equal.
Hence the correct option is A. and D.
(4) Here the correct option will be A.

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