Moving a block with kinetic and static friction to find the net force?

Click For Summary
The discussion focuses on calculating the net force acting on a block when it transitions from static to kinetic motion. The coefficient of static friction is 0.37, and the coefficient of kinetic friction is 0.14, with the block's mass being 3.4 kg. To find the force required to initiate movement, the maximum static friction force is calculated using the formula μs * m * g. Once the block starts moving, the net force is determined by subtracting the kinetic friction force from the static friction force. The conversation emphasizes understanding the transition between static and kinetic friction to solve the problem effectively.
disque
Messages
29
Reaction score
0
The coefficient of static friction between a block and a horizontal floor is 0.37, while the coefficient of kinetic friction is 0.14. The mass of the block is 3.4 kg. If a horizontal force is slowly increased until it is barely enough to make the block start moving, what is the net force on the block the instant that it starts to slide?

I tried multiple ways of solving this problem, but am only down to one attempt left for credit on my homework. I don't know if I'm over analyzing the problem or what, but its giving me trouble, please help. Thank you
 
Physics news on Phys.org
What force is required to move the block? Or more specifically what is the greatest amount of resistance the static friction can provide?

μs*m*g

But that's the static friction. But that is the first part of what you want.

After it moves then it is opposed by the μk*m*g of the kinetic friction, so ... Your net force then is Fstatic - Fkinetic.
 
thanks again I owe you!
 
Thread 'Correct statement about size of wire to produce larger extension'
The answer is (B) but I don't really understand why. Based on formula of Young Modulus: $$x=\frac{FL}{AE}$$ The second wire made of the same material so it means they have same Young Modulus. Larger extension means larger value of ##x## so to get larger value of ##x## we can increase ##F## and ##L## and decrease ##A## I am not sure whether there is change in ##F## for first and second wire so I will just assume ##F## does not change. It leaves (B) and (C) as possible options so why is (C)...

Similar threads

  • · Replies 6 ·
Replies
6
Views
1K
Replies
61
Views
3K
Replies
16
Views
3K
Replies
12
Views
2K
Replies
7
Views
1K
  • · Replies 7 ·
Replies
7
Views
1K
Replies
6
Views
1K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 10 ·
Replies
10
Views
2K
Replies
13
Views
2K