How Do You Calculate Frictional Force on a Block?

[mdawg467]

Homework Statement

A 3-lb horizontal force is applied to a 10-lb block on a rough horizontal surface. The block is initially at rest. If [itex]\mu[/itex]_s is 0.5 and the [itex]\mu[/itex]_k is 0.4, the frictional force on the block is?

Homework Equations

F_N=mg
F_k=[itex]\mu[/itex]_kF_N
F_s,max=[itex]\mu[/itex]_sF_N

The Attempt at a Solution

I found [itex]\mu[/itex]_s,max required to move the 10-lb block was 49.0 lb/ms^2..or approximately 22N.

Since the force being applied is 3-lb, or approximately 1.4N, then the frictional force must be equal to the force being applied correct?

Thanks.

 

[PeterO]

Homework Statement

A 3-lb horizontal force is applied to a 10-lb block on a rough horizontal surface. The block is initially at rest. If [itex]\mu[/itex]_s is 0.5 and the [itex]\mu[/itex]_k is 0.4, the frictional force on the block is?

Homework Equations

F_N=mg
F_k=[itex]\mu[/itex]_kF_N
F_s,max=[itex]\mu[/itex]_sF_N

The Attempt at a Solution

I found [itex]\mu[/itex]_s,max required to move the 10-lb block was 49.0 lb/ms^2..or approximately 22N.

Since the force being applied is 3-lb, or approximately 1.4N, then the frictional force must be equal to the force being applied correct?

Thanks.

Sounds good - especially in America where apparently the pound is a unit of Force, not a unit of mass.

 

[mdawg467]

Thank you!
Yeah only here in America haha..