What is the magnitude of the frictional force acting on the crate?

[moondawg]

Homework Statement

A crate with a total mass of 50 kg is initially at rest on a level floor. A horizontal force of 150N pushes the crate across the floor at a constant acceleration of 1.2m/s². What is the magnitude of the frictional force acting on the crate?

Homework Equations

The Attempt at a Solution

So this question seems so basic but I know I'm doing it wrong. All i did was plugged the numbers into the F=$$\mu$$N formulas and got $$\mu$$= .31. But in using that formula I am not even taking into account the acceleration and I don't know what to use in order to take it into account?! Someone please explain

 

[Stonebridge]

It's just F=ma on the crate, but remembering that there are 2 forces acting here; the 150N and the friction.

 

[ThyQuotidian]

 

[a.ratnaparkhi]

It means that if 50N force is foreword,then frictional force must act backward.
let net force be fn.
so according to the free body diagram,
fn=150-f (say frictional force be f) ...1

fn=ma=50*1.2
Now from this you'll get fn & from equation 1, you'll get f.

 

[rwisz]

The magnitude of the frictional force acting on the crate can be calculated using the equation F = μN, where μ is the coefficient of friction and N is the normal force (perpendicular to the surface) acting on the crate. However, in this case, the crate is accelerating, so the frictional force is not constant and cannot be determined using this formula alone.

To find the magnitude of the frictional force in this situation, we need to use the equation F = ma, where F is the net force acting on the crate, m is the mass of the crate, and a is the acceleration of the crate. In this case, the net force is the horizontal force of 150N, so we can rearrange the equation to solve for a:

a = F/m
a = 150N/50kg
a = 3m/s^2

Now, we can use this value for acceleration in the equation F = ma to find the magnitude of the frictional force:

F = ma
F = (50kg)(3m/s^2)
F = 150N

Therefore, the magnitude of the frictional force acting on the crate is 150N. This means that the crate experiences a frictional force of 150N in the opposite direction of its motion, causing it to accelerate at a rate of 1.2m/s^2.