# Calculate the acceleration of the block

A 0.5 kg block is being slid up a chalkboard with an applied force of 6.0 N upward and 2.0 N inward towards the board. If the coefficient of kinetic friction is 0.4.

a) Calculate the force of friction.

b) Calculate the acceleration of the block.

F = mju R [ F = u R]

1. F/u = 6/0.4 = 15N ???

2. F = ma ..... 6/0.5 = a = 12m/s^2

not sure... some1 back me up on this!

Last edited:

no one helping

Doc Al
Mentor
If you would like help, show what you've done so far--per PF rules.

Start by identifying all the forces acting on the block.

If you would like help, show what you've done so far--per PF rules.

Start by identifying all the forces acting on the block.
F = mju R [ F = u R]

1. F/u = 6/0.4 = 15N ???

2. F = ma ..... 6/0.5 = a = 12m/s^2

not sure... some1 back me up on this!

Show us your attempts at solving this problem first.

Show us your attempts at solving this problem first.

2. (6-(2*0.4))/0.5= 10.4 upwards w.r.t board.

(6-(2*0.4)-(0.5*9.8))/0.5=0.6 upwards w.r.t ground.

Doc Al
Mentor
F = mju R [ F = u R]
I assume F is the friction force? So what is R?

I assume F is the friction force? So what is R?

sorry
mean Fn

If you would like help, show what you've done so far--per PF rules.

Start by identifying all the forces acting on the block.

can u help now

Doc Al
Mentor
Seems like you have several versions of solutions. Approach it systematically: What forces act on the block? What's the force of friction?

Seems like you have several versions of solutions. Approach it systematically: What forces act on the block? What's the force of friction?

can u help me
which formula i need to use first one

hage567
Homework Helper
For (1), use the formula you've already stated, F=uN. Do you know what force N is in this case? (I think you were calling in R in your first post)

For (1), use the formula you've already stated, F=uN. Do you know what force N is in this case? (I think you were calling in R in your first post)
I AM NOT SURE
CAN U DO THAT.

hage567
Homework Helper
N is the normal force. The block is being pushed against a vertical wall. So which of the two forces you were given in the question is holding the block on the wall? That is the force you need to use to find the force of friction.

N is the normal force. The block is being pushed against a vertical wall. So which of the two forces you were given in the question is holding the block on the wall? That is the force you need to use to find the force of friction.

i need help in B

Doc Al
Mentor
i need help in B
So you have finished A and correctly calculated the force of friction? If so, good.

To solve B, identify all the forces acting on the block. Then find the net force and use that to calculate the acceleration via Newton's 2nd law.