need help in physics plz?

Question

i had a test and we had these questions i dont think i got it right so can someone plz explain this problem how to solve it step by step.thank you

1a) The force of a friction acting on a sliding crate is 155N.
how much force must be applied to maintain a constant velocity?answer in units of N.

b)what will be the net force acting on the crate?answer in units of N.

2)a race car travels along a raceway at a constant Velocity of 200km/h.
what is the net force acting on the car.

Answer 1

1. a) If sum of forces on the body is 0 the body is either at rest or moving with a constant speed.
1b) F=0
since F(forward)=f(friction)
2. F(net)=0
Force produced by the engine is balanced out by forces of air resistance, frictions and all that makes the car to stop moving)
F(engine)=F(air drag,....)

Answer 2

1) the Force must be 155N in order for the v to be constant (0m/s)

2) its a constant v therefore theres no acceleration