Physics Forces, newtons, static, kinetic o my?

Question

60kg crate rests on level floor. coefficients of static and kinetic friction are .760 and .410 respectively. What horizontal pushing force is required to (a) just start the crate moving (b) slide the crate across the dock at a constant speed?

For this one I got (a) = 429 N and (b)=226N
?

Is a net force being applied to an object when the object is moving downward
(a) with a constant acceleration of 9.8m/s^2
(b) with a constant velocity of 9.8 m/s^2?
Reasoning?

Stack of books 165Newtons are placed on a scale in an elevator. scalre reads 165N. can u tell from this info whether the elevator is moving with constant velocity of 2m/s upward or 2m/s downward or whether the elevator is at rest? explain

Answer 1

Crate: I don't get your answers.
a) To get it moving, you need to overcome the static friction. That friction is
Ffs = mus*N
where N is the normal force. Since the floor is level, that's just the weight.
Ffs = .76*60 kg*9.8 m/s^2

Note: 1 N = 1 kg*m/s^2

b) Once it's moving, to keep it going at constant speed you need to offset kinetic friction. No more no less since to go at constant speed you need a net force of zero.

Ffk = muk*N
Ffk = muk*m*g

net force:
a) A net force is required to have an acceleration.
b) Net force must be zero if velocity is constant.

elevator:
Can't tell. Could be any of the above. If velocity is constant, acceleration is zero; if accelration is zero, net force is zero.