(a) The answer would be 650 N [fwd]. Why? Newton's Third Law States for every action there is an equal and opposite reaction. Also, since Fnet is equal to zero all forces are balanced out. Still don't get it? Draw an FBD stare at it and process all the words I just wrote. Trust me its easier than you make it;)
(b) Still working on it....
A 1200 kg car pulls an 820 kg trailer over a rough road. The
force of friction acting on the trailer is 650 N [backwards].
Calculate the force that the car exerts on the trailer if
(a) the trailer is moving at a constant velocity of
30 km/h [forward]
(b) the trailer is moving at a constant velocity of
60 km/h [forward]
(c) the trailer is moving forward at 60 km/h and starts
accelerating at 1.5 m/s2 [forward]
(d) the trailer is moving forward at 60 km/h and starts
accelerating at 1.2 m/s2 [backwards]
4 answers
b)also 650N [forward] because constant velocity means Fnet is 0.
Mama
T*3=4