# Homework Help: Find the magnitude of a block pulling a 200 lb block

1. Oct 29, 2006

### the_d

I have to find the magnitude of a block pulling a 200 lb block up a plane of angle 30 degrees with an acceleration of 4.0425 ft/s^2, the coefficient of kinetic friction is 0.2. Where should I start?

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Last edited: Oct 29, 2006
2. Oct 29, 2006

### andrevdh

The sum of all of the forces acting on the block in the direction of the incline need to be equal to its mass times its acceleration.

3. Oct 29, 2006

### the_d

ok so for the x and y direction EF = ma then what?

4. Oct 29, 2006

### the_d

ok so for the x and y direction EF = ma then what?

5. Oct 29, 2006

### andrevdh

You need to add the forces in the direction of the incline and divide them by the mass of the block to get the given acceleration.

The sum of the forces perpendicular to the incline need to add up to zero.

6. Oct 29, 2006

### the_d

ok i got those, so now how do i find? the weight of the block thats pulling? the only force on it is its (mass) * (gravity)

7. Oct 29, 2006

### andrevdh

There are at least four forces in operation!

The weight, friction, the required pulling force up the incline and the normal force.

8. Oct 29, 2006

### the_d

ok, thanks for ur help

9. Oct 30, 2006

### andrevdh

You first need to determine the size of the pulling force, $$P$$, on the block on the incline in order to solve the problem.