Block on incline with vertical force

[robvba]

Homework Statement

3.0-kg block slides on a frictionless 37° incline plane. A vertical force of 15 N is applied to the block. The acceleration of the block is?

Homework Equations

m*g*sin()

The Attempt at a Solution

3*9.8*sin(37) - 15 = 2.7

 

[mathmate]

Assuming the vertical force is downwards, then the acceleration of the block is downwards along the incline. It would be more relevant to resolve forces along the incline.

The downward force and the weight of the block are in the same direction, so your expression for the weight applies equally to the downward force. The mass is 3kg.
So if you use Newton's second law F=ma, you would be able to figure out the acceleration, assuming the inclined plane is frictionless.

 

[Doc Al]

What forces act on the block? What are their components parallel to the incline? What's the net force parallel to the incline?

 

[robvba]

The figure shows a block on a 37 degree incline with a vertical arrow moving from the block upward (representing the applied force)

 

[Doc Al]

The figure shows a block on a 37 degree incline with a vertical arrow moving from the block upward (representing the applied force)

OK, so the vertical force is upward. What is its component parallel to the incline? What is the component of the weight parallel to the incline?

 

[robvba]

OK, so the vertical force is upward. What is its component parallel to the incline? What is the component of the weight parallel to the incline?

m*g*sin()

 

[Doc Al]

m*g*sin()

That's the component of the weight. (Does it point up or down the incline?) What about the component of the applied vertical force?

 

[robvba]

That's the component of the weight. (Does it point up or down the incline?) What about the component of the applied vertical force?

It points down. The applied points up.

 

[Doc Al]

It points down. The applied points up.

Good. What's the component of the applied force parallel to the incline?

 

[robvba]

Good. What's the component of the applied force parallel to the incline?

m*g*cos()?

 

[mathmate]

? ?