Static and Kinectic Problem Help

[globalcrook]

Homework Problem

A Worker is pulling a box and applies a force at an angle of 45 degress to the horizontal, how large must the force be to move the box

FBD:

n
| /
| / <----Angle in between is 45 degrees
O ------F cos 45
|
|
mg

Please help, confused about how to solve this problem
Thanx in advance

 

[Locrian]

Well since they didn't give you any values (I assume), you are going to leave everything as variables. Break the force down into components first, find the component in the x-direction necessary to be greater than the force of static friction, then rebuild your original force knowing that value.

Try it and post when you get stuck.

 

[kyle8921]

I would approach this problem by first understanding the concepts of static and kinetic friction. Static friction is the force that prevents an object from moving when a force is applied to it. Once the applied force overcomes the static friction, the object starts moving and kinetic friction takes over.

In this problem, the worker is pulling the box with a force at an angle of 45 degrees to the horizontal. This means that the applied force can be broken down into two components - one along the horizontal direction and one along the vertical direction.

To move the box, the applied force must overcome the static friction between the box and the surface it is on. This can be calculated using the formula F = μsN, where μs is the coefficient of static friction and N is the normal force acting on the box.

Since the box is not moving, the force of gravity (mg) must be equal to the normal force (N). Therefore, the equation becomes F = μsmg.

Now, we need to find the minimum force required to overcome the static friction. This can be done by substituting the angle of 45 degrees into the equation Fcos45 = μsmg, which gives us the equation F = μsmg/cos45.

To solve for F, we need to know the coefficient of static friction for the surface the box is on. This information is not provided in the problem, so we cannot give a specific answer. However, we can use the value of μs to find the minimum force required to move the box.

I would also like to point out that this problem assumes that the box is on a flat, frictional surface. If the surface is not flat or has a different coefficient of friction, the calculations may be different. It is important to understand the concepts and assumptions behind a problem before attempting to solve it.

In conclusion, to solve this problem, we need to understand the concepts of static and kinetic friction and use the equations and assumptions to find the minimum force required to move the box. I hope this explanation has helped in understanding the problem.