This question came up on my review package tonight, and it has me stumped.
"A box of mass 14.5kg slides at a constant speed of 4.70m/s down a ramp at 35.3 degrees below the horizontal. What is the force of friction on the box?"
I can calcuate force of friction on accelerating objects, but one moving at a constant speed has me puzzled. Also, my FBD Fgx and Fgy components look a little suspicious. I got:
Fgy=142.1 N
Fgx=79.6 N
Can anyone help clear this up for me?
Thanks so much.
If there is no acceleration, the component of weight down the ramp, M g sin 35.3, equals the friction force.
The speed does not matter in the calculation.
I do't see how you got your Fgy and Fgx umbers.
Yeah, me either. *sigh* Thanks very much.
yeah
Certainly! I can help you understand how to solve this problem.
To find the force of friction on the box, we need to understand the forces acting upon it.
Let's start by drawing a free-body diagram (FBD) of the box on the ramp. The force of gravity (Fg) can be broken down into two components: Fgx (the component of Fg parallel to the ramp's surface) and Fgy (the component of Fg perpendicular to the ramp's surface).
Now, since the box is sliding down the ramp at a constant speed, we know that the net force acting on the box must be zero. This means that the force of friction (Friction) must balance out the component of the gravitational force parallel to the ramp's surface.
In this case, Fgx represents the component of Fg parallel to the ramp's surface and is equal to Fgx = Fg * sin(θ), where θ is the angle of the ramp (35.3 degrees). So, Fgx = 142.1 N * sin(35.3 degrees) ≈ 81.45 N.
Since the box is sliding down the ramp at a constant speed, we can conclude that the force of friction is equal in magnitude but opposite in direction to Fgx, given by Friction = -Fgx. Therefore, Friction ≈ -81.45 N.
So, the force of friction on the box is approximately -81.45 N. The negative sign signifies that the force of friction acts in the opposite direction to the motion of the box.
I hope this explanation helps clarify the problem for you! If you have any further questions, feel free to ask.