daiea08 said:Homework Statement
How hard do you need to push a 2kg box which has .2 coefficient of kinetic friction so that it moves with a constant speed of 5m/s?
[The Attempt at a Solution
(I'm calling g 10m/s2 not 9.8)
F(kinetic friction)=(.2)Fn=(.2)mg=(.2)(20N)=4N
so...since the acceleration is zero, the force must equal 4N..so 4N is the answer? If I'm correct then in the "5m/s" just a deterrent? Is the key point "constant speed?"
I'd say you were correct. The 5 m/s was just to throw you off!daiea08 said:so...since the acceleration is zero, the force must equal 4N..so 4N is the answer? If I'm correct then in the "5m/s" just a deterrent? Is the key point "constant speed?"
Doc Al said:I'd say you were correct. The 5 m/s was just to throw you off!
The problem could be worded better as it implies you are supposed to figure out how to get it to 5 m/s from some unspecified prior condition. But you aren't given any info as to its initial speed or the time needed to get the final speed, so you can't answer that.
Sure.malty said:Yeah, that was my initial though too, and tbh I'm a little rusty with this stuff, but what would happen if a force in excess of 4N was applied wouldn't its velocity increase i.e accelerate?
The mass of the box has a direct relationship with the force needed to move it at a constant speed. The greater the mass of the box, the more force is required to overcome its inertia and move it at a constant speed.
Yes, the surface on which the box is being pushed can greatly affect the amount of force required to move it at a constant speed. Rough surfaces create more friction, which requires more force to overcome and move the box at a constant speed.
Yes, the angle at which the box is being pushed can affect the force needed to move it at a constant speed. Pushing the box at an angle reduces the effective force in the direction of motion, making it harder to move the box at a constant speed.
The speed at which the box is being pushed does not affect the force required to maintain a constant speed. Once the box is in motion, it will continue moving at a constant speed unless acted upon by an external force.
Yes, there is a maximum force that can be applied to move the box at a constant speed. This maximum force is dependent on the mass of the box and the coefficient of friction between the box and the surface it is being pushed on.