Find the coefficient of kinetic friction between the crate and the surface

In summary, the conversation was about finding the coefficient of kinetic friction between an apple crate and a horizontal surface, given its weight, acceleration rate, and pulling force at a specific angle. Strategies for solving the problem were discussed, including using the equations F = m*a and the relationship between the force of friction, coefficient of friction, and normal force. The final solution was successfully found.
  • #1
hannsparks
32
0
Coefficient of kinetic friction

I have a mojor physics test thursday (two days) and here is a pretest question that I cannot figure out if anyone can figure it out I'd greatly appreciate it. I actually know what the answer is uk=0.253 I just don't know how to get that answer.
" An apple crate with a weight of 49 N accelerates at a rate of 0.5 m/s2 along a horizontal surface as the crate is pulled with a force of 14.5 N as shown in Figure 1. The angle at which the crate is being pulled is 19 degrees.
Find the coefficient of kinetic friction between the crate and the surface."

heres my attempt: N=49+Fsin19 y direction
Fcos19-uk=(5)(0.5) x direction
I then tried to combine the two equations to figure out N and F but I am stuck.
 
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  • #2
First of all is the angle 19, the angle over the horizontal or under? If it is over then you have to write that N=49-Fsin19 . Also, uk isn't a force, N*uk is the force of friction.
 
  • #3
Draw a picture and label the forces.

If the create is accelerating there must be a net force (F = m*a).
You know that a 14.5 N force is being exerted on the box at 19 degrees. What part of this 14.5 N is going to accelerate the box horizontally? What part tries to accelerate it vertically?

Remember,
The force of friction = coefficient of friction * normal force.
The force of friction points in the opposite direction of motion.
 
  • #4
im so confused I have no idea what to do next.. do I know have to combine the two equations to figure out N and F?
 
  • #5
hey guess what..I figured it out! Thanks for all your help :)
 

FAQ: Find the coefficient of kinetic friction between the crate and the surface

What is the coefficient of kinetic friction?

The coefficient of kinetic friction is a dimensionless quantity that represents the amount of resistance between two surfaces in contact when one of the surfaces is in motion.

How is the coefficient of kinetic friction calculated?

The coefficient of kinetic friction is calculated by dividing the force of kinetic friction by the normal force between the two surfaces. It can also be calculated by measuring the acceleration of the object and using the equation μk = a/g, where μk is the coefficient of kinetic friction, a is the acceleration, and g is the acceleration due to gravity.

What factors affect the coefficient of kinetic friction?

The coefficient of kinetic friction can be affected by several factors, such as the roughness of the surfaces in contact, the weight of the object, and the type of material the surfaces are made of. It can also vary with the temperature and speed of the object.

Why is it important to know the coefficient of kinetic friction?

Understanding the coefficient of kinetic friction is crucial in many real-world applications, such as designing brakes for vehicles, determining the force needed to move an object, and predicting the behavior of objects in motion. It also helps in minimizing energy loss and preventing accidents.

How can the coefficient of kinetic friction be measured?

The coefficient of kinetic friction can be measured using various methods, such as the inclined plane method, the spring scale method, and the drop height method. These involve measuring the force needed to move an object on a surface and using it to calculate the coefficient of kinetic friction.

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