I need help with physics...please!!!!!!?

Question

The question reads: A force of 154 N is used to acelerate a 15.4 kg box across the floor at a rate of 3.25 m/s^2. What is the coefficient of friction between the box and the floor?

Could someone please explain to me how to do this problem...

Please explain in own words cuz I have the notes my teacher gave us I just don't understand cuz he doesn't explain anything right.

Answer 1

Fnet = ma

Fnet is the sum of forces, which are Fapply and Friction

Fapply - Friction = ma
154 - Friction = (15.4)(3.25)
154 - Friction = 50.05
Friction =103.95

Friction = u(Fnormal)
Fnormal is equal to Fweight

103.95 = u (15.4 * 9.8)
u =.6888

Answer 2

Break up the forces into components.

I always look at the y-direction first.

Forces in the y-direction

N = normal force
W = -mg (Weight - negative since it is down)

Since the box is not moving up or down, the acceleration in the y-direction is 0.

So

N - mg = 0
N = mg = 15.4 * 9.8 = 150.92 N


In the x-direction, the forces are

F = 154 (This is our applied force)
f = -μ * N (This is the frictional force - Negative since friction is always opposite the direction of motion)

That's it.

However, we are accelerating in this problem. So when we sum up the forces, we must set it equal to m*a

F - f = ma

154 - μ N = ma
154 - μ * 150.92 = 15.4 * 3.25

Solving for μ = 0.6888. The coefficient of friction has no units.

Answer 3

154 N acting on 15.4 kg should produce an acceleration of 10m/s² but, instead, it's only 3.25m/s². The difference (104N) must be made up by friction. Since the box has mass 15.4 kg and is being accelerated by 9.8 m/s² it has a total normal force of 150.92 N and the ratio of those is the coefficient of dynamic friction.
104/150.92 = .39

Doug


Doug

Answer 4

F=154N
m=15.4kg
a=3.25ms^2

friction always acts opposite to applied force.
therefore net force acting is (F-friction) which accelerates the body. overall equation is

F-friction=mass*acceleration
154-friction=15.4*3.25
friction=154-(15.4*3.25)
=154-50
=104N

friction=coeffecient of friction* normal force
coeffecient of friction= friction/ normal force
=104/15.4*9.8
=0.6891

Answer 5

You have to realize that it's kinetic friction, and that the total force is F -friction = ma
You have F, m, and a.
F - (coefficient)mg = ma
switch the friction and ma
154-(15.4)(3.25) = (coefficient) x (15.4)(9.8)
divide both sides by 15.4x9.8 to find the coefficient.

Answer 6

http://regentsprep.org/Regents/physics/phys01/friction/default.htm

Try this it explains it fairly well.