Word problem for physics...forces & friction?

Question

A sled of mass 50 kg is pulled along snow-covered, flat ground. The static friction coefficient is 0.30, and the sliding friction coefficient is 0.10. What force is needed to get the sled moving? Then, what force is needed to keep the sled moving at a constant velocity? And once moving, what total force must be applied to the sled to accelerate it 2.0 m/s2?

Answer 1

to over come static friction
F=50*9.8*0.3
F=147 N

To move at constant speed
F=50*9.8*0.10
F=49 N

To accelerate at 2 m/s^2

F-49=50*2
F=51 N

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Answer 2

It requires more work to get something moving than it does to keep it moving. Static coefficient of fric is for a stationary object. Sliding friction is a non-stationary (sliding) object. Ff=(Coefficient of friction)*(Normal Force) normal force is mass times gravity (9.81). With that in mind...

What force is required to get the sled moving?

so we use the static coefficient and plug it in to the equation for frictional force.

(.3)*(50*9.81)=147.15N is the force required.

What force is needed to keep it moving at a constant velocity?

(.1)*(50*9.81)=49.05N is the force required.

What force is required to keep it accelerating at 2m/s^2?

50.95 (using the equations above)