Newton first and second law

[Beretta]

To drag a 75kg log along the ground at constant velocity, you have to pull in it with a horizontal force of 250N. a) what is the resistive force exerted by the ground? b) what horizontal foce must you exert if you want to give the log an acceleration of 2m/s^2?
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a) Is it 250N because of the constant acceleration?

b)
F = m*a
a = 2 m/s^2 and m = 75kg gives F = 150 N that must be 150 N over the 250 N the ground resists. so you must drag 400 N

Please help me out!

 

[HallsofIvy]

Originally posted by Beretta
To drag a 75kg log along the ground at constant velocity, you have to pull in it with a horizontal force of 250N. a) what is the resistive force exerted by the ground? b) what horizontal foce must you exert if you want to give the log an acceleration of 2m/s^2?
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a) Is it 250N because of the constant acceleration?

NO, it's 250N because of the constant SPEED! The acceleration is 0 so the "net" force is 0.

b)
F = m*a
a = 2 m/s^2 and m = 75kg gives F = 150 N that must be 150 N over the 250 N the ground resists. so you must drag 400 N

Please help me out!

Exactly right.

 

[Beretta]

First and second law

Thank you very much :)