How to Find Force of Friction and Acceleration?

In summary: Once you determine that the object does not move, you can then use the formulas for kinetic and static friction to calculate the acceleration.
  • #1
Thomas10
2
0

Homework Statement


Hey, guys I'm having trouble solving this problem, I'm not sure what to do first
This is the info it gives:
A stationary 15 kg object is located on a table near the surface of the earth. The coefficient of static friction between the surfaces is 0.40 and the coefficient of kinetic friction is 0.25.
This is the problem:
A horizontal force of 20 N is applied to the object.
A)Determine the force of friction.
B)Determine the acceleration of the object.

Homework Equations


F=MA
F=uN
W=MG

The Attempt at a Solution


For this part A of this problem I wasn't sure if this was right but what I did was I first found the weight which is 15x9.81=147.15 I then got confused since the problem gives coefficient of static and kinetic since I thought the object was moving I used the formula F=uN and used the coefficient of kinetic friction so .25 times the weigh 147.15 and then I got 36.7875 I'm not sure if this is the right answer for part b to find the force of friction.

For part B of this problem I completely don't know what to do I thought that 20N was a force I can plug in for F=MA so I thought I can divide 20 by 15 which is the weight to find acceleration
 
Physics news on Phys.org
  • #2
When a force is applied to an object that is in resting contact with a surface, the first question is whether it will move relative to the surface. For that you must use the static coefficient. The static coefficient tells you the maximum frictional force available. The actual frictional force will never exceed the net of the other applied forces.
If the static frictional force is insufficient to withstand the net applied force, then the object will move and the frictional force should be calculated using the kinetic coefficient.
 
  • #3
haruspex said:
When a force is applied to an object that is in resting contact with a surface, the first question is whether it will move relative to the surface. For that you must use the static coefficient. The static coefficient tells you the maximum frictional force available. The actual frictional force will never exceed the net of the other applied forces.
If the static frictional force is insufficient to withstand the net applied force, then the object will move and the frictional force should be calculated using the kinetic coefficient.
I get part A of my problem but now how do I find the acceleration of the object?
 
  • #4
Thomas10 said:
I get part A of my problem
I don't think you do. If you did, you would be able to answer part B easily.
As I wrote in post #2, your first step must be to determine whether the object moves at all. Please post your working for that.
 

Related to How to Find Force of Friction and Acceleration?

1. What is the formula for calculating force of friction?

The formula for calculating force of friction is: Ff = μN, where Ff is the force of friction, μ is the coefficient of friction, and N is the normal force.

2. How do you determine the coefficient of friction?

The coefficient of friction can be determined by dividing the force of friction by the normal force. It can also be found by conducting experiments and measuring the force of friction at different weights and surfaces.

3. What factors affect the force of friction?

The force of friction is affected by the type of surface, the weight of the object, and the coefficient of friction between the two surfaces. Rougher surfaces and heavier objects tend to have a higher force of friction.

4. How do you find the acceleration of an object with friction?

To find the acceleration of an object with friction, you must first calculate the net force acting on the object by subtracting the force of friction from the applied force. Then, use Newton's second law (F = ma) to calculate the acceleration.

5. Can the force of friction be greater than the applied force?

No, the force of friction cannot be greater than the applied force. The force of friction always acts in the opposite direction of motion, so it can only ever be equal to or less than the applied force.

Similar threads

  • Introductory Physics Homework Help
Replies
6
Views
555
  • Introductory Physics Homework Help
Replies
6
Views
1K
  • Introductory Physics Homework Help
Replies
7
Views
365
  • Introductory Physics Homework Help
2
Replies
42
Views
971
  • Introductory Physics Homework Help
Replies
11
Views
2K
  • Introductory Physics Homework Help
Replies
9
Views
740
  • Introductory Physics Homework Help
Replies
8
Views
924
  • Introductory Physics Homework Help
Replies
30
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
666
Replies
24
Views
1K
Back
Top