Frictional force, normal force and coefficient of friction

[lisa1991]

Homework Statement

Calculate the frictional force, normal force and coefficient of friction for an 0.2kg object that is lying on a 35 degree incline.

Homework Equations

Ff= u x Fn
F= m x a

The Attempt at a Solution

I managed to get FN= m x a x cos# = -9.81 x 0.2 x cos35 = 1.61 N

I have no idea how to get Ff, but when I work that out I will be able to work out coefficient (u). Thanks for any help

 

[tms]

Since the block is not accelerating, the net force must be zero. Look at all the forces, and find their components along the incline and normal to it.

 

[lisa1991]

sorry also should have mentioned that 35 degrees is the angle the object starts to move down the slope

 

[NascentOxygen]

sorry also should have mentioned that 35 degrees is the angle the object starts to move down the slope

Hi lisa1991! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

At 35° the component of gravity overcomes friction, so the forces are equal and opposite. Draw a diagram showing the incline and the direction of the forces involved.

 

[asteriatic]

.


I would approach this problem by first understanding the concepts of frictional force, normal force, and coefficient of friction. Frictional force is the force that opposes the motion of an object, and it is dependent on the normal force and the coefficient of friction. The normal force is the force exerted by a surface on an object in contact with it, and it is perpendicular to the surface. The coefficient of friction is a constant that represents the roughness of the surfaces in contact and determines the strength of the frictional force.

In this problem, we have an object with a mass of 0.2kg on a 35 degree incline. To calculate the frictional force, we can use the equation Ff = u x Fn, where u is the coefficient of friction and Fn is the normal force. We have already calculated the normal force to be 1.61 N, so now we need to find the coefficient of friction.

To find the coefficient of friction, we can use the equation F = m x a, where F is the net force acting on the object, m is the mass of the object, and a is the acceleration. In this case, the net force is equal to the sum of the forces in the direction of motion, which is the force of gravity (mg) and the frictional force (Ff). Therefore, we can write the equation as F = mg + Ff.

Since the object is on an incline, we need to use the component of gravity that is acting parallel to the incline, which is mg sin# (where # is the angle of the incline). So, the equation becomes ma = mg sin# + Ff. We can rearrange this to solve for Ff: Ff = ma - mg sin#.

Now, we have all the information we need to calculate the frictional force. Plugging in the values, we get Ff = (0.2 kg)(9.81 m/s^2) - (0.2 kg)(9.81 m/s^2)(sin35) = 1.23 N.

Finally, we can use the equation Ff = u x Fn to solve for the coefficient of friction. Plugging in the values, we get 1.23 N = u (1.61 N), which gives us a coefficient of friction of approximately 0.77.

In conclusion, the frictional force for an