An 900 kg purple pickup truck tows a small 400 kg trailer using a relatively lig

Question

An 900 kg purple pickup truck tows a small 400 kg trailer using a relatively lightweight tow rope as shown in the animation. The position of the trailer is given in m and time is in s.
a) What is the magnitude of the net force on the entire system (truck and trailer)? N b) Which is greater, the force of the truck on the trailer or the force of the trailer on the truck?
the force of the truck on the trailer
the force of the trailer on the truck
neither, the force of the truck is equal in magnitude to the force of the truck on the trailer
c) What force on the truck is in the direction of the acceleration of the truck and makes the largest contribution to the net force on the truck?
force of static friction of the road on the truck's tires
force of the tow rope on the truck
force of the air (as a reaction to the truck's exhaust) on the truck; (i.e. thrust, just like the force that propels the space shuttle on liftoff)
force of the truck's engine on the truck

d) What is magnitude of the net force on the trailer? N
e) What is the magnitude of the net force on the truck? N (f) Suppose the tow rope bends easily. If the truck slows to a stop, describe the motion of the trailer.
The trailer will continue accelerating with the same instantaneous acceleration that it had when the truck began to slow down and then crash into the back of the truck.
The trailer will slow to a stop with the same acceleration (negative!) as the truck.
The trailer will travel at a constant velocity equal to its instantaneous velocity when the truck began to slow down and then crash into the back of the truck.
The car'v velocity will instantaneously go to zero.

Explanation / Answer

a) The net force on the whole system can be calculated from the total mass and acceleration(F = ma). If the truck/trailer is moving at a constant velocity, then there is no net force. b) Newton's Third Law: If body A exerts a force F on body B, then body B exerts a force of -F on body A c) Process of elimination - the tow rope is pulling in the opposite direction, so not that one. If the exhaust were the major factor, cars wouldn't be able to reverse, so not that one either. d) Like a), F = ma e) see d) f) Newton's First Law. No force, thus no acceleration. Velocity remains constant

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