Box sliding down wall at constant speed

In summary, the conversation discusses a problem involving a 2.0 kg wood box sliding down a vertical wood wall while being pushed at a 45 degree angle. The problem requires the use of the equation ΣFY = FPY - mg to determine the correct force needed to keep the box in constant velocity. However, the solution provided by the person asking the question did not take into account the friction component, which acts against the relative motion of the box and the wall. The correct equation should be F(push)sin45 - mu*N - mg = 0, where mu is the coefficient of friction and N is the normal force.
  • #1
ayjakk
3
0

Homework Statement


The 2.0 kg wood box in the figure slides down a vertical wood wall while you push on it at a 45 ∘angle.
https://session.masteringphysics.com/problemAsset/1070374/4/06.P51.jpg

Homework Equations


ΣFY = FPY - mg

The Attempt at a Solution


I know that since there is a constant velocity, the acceleration will be zero. I then have
0 = FPsin45 - mg
FPsin45 = mg
FP = (mg)/sin45
FP = ((2kg)*(9.8m/s2))/sin45
FP = 27.719 N

Which is wrong. Am I correct in assuming that the only forces in the Y direction (taking up as positive Y) are the y-component of the pushing force and gravity? What am I missing here?
 
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  • #2
Your approach just misses the friction component which acts against the relative motion of box/wall (i.e. downwards).. Therefore the equation will be

F(push)sin45 - mu*N - mg = 0 ; where mu is coefficient of friction and N= F(push) cos 45 ...
 

1. What is the force acting on the box as it slides down the wall at constant speed?

The force acting on the box is the force of gravity pulling it down towards the ground. This force is counteracted by the normal force of the wall pushing back on the box.

2. How does the incline of the wall affect the speed of the box?

The incline of the wall does not affect the speed of the box, as long as the box is sliding at a constant speed. This is because the forces acting on the box, such as gravity and the normal force, are balanced and cancel each other out.

3. Does the mass of the box play a role in the speed at which it slides down the wall?

Yes, the mass of the box does play a role in the speed at which it slides down the wall. A heavier box will experience a greater force of gravity, causing it to slide down the wall at a faster speed compared to a lighter box.

4. Why does the box not fall straight down instead of sliding down the wall?

The box does not fall straight down because there is a force acting on it from the wall. This force is the normal force, which is perpendicular to the wall and prevents the box from falling straight down.

5. How can we calculate the speed of the box as it slides down the wall at constant speed?

The speed of the box can be calculated using the formula v = d/t, where v is the speed, d is the distance the box slides down the wall, and t is the time it takes for the box to slide down. Since the speed is constant, the distance and time can be measured at any point during the sliding motion.

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