please help!!!!

Question

1) on the figure below draw the free body diagram for ...

A) a box being push across a table with friction and a positive acceleration to the right

b) on the figure below draw the free body diagram for a box sliding up a ramp with friction at a constant speed

I cant actually add a picture to this but the figure for a is just a rectangle

and for figure b it is a rectangle but tilted like this /

Answer 1

A free body diagram contains arrows representing forces acting on the blocks.

The direction of each arrow shows the direction of the force, and

the length of the arrows shows relative sizes.

A) There are three forces.

1. Gravity: The force of gravity always points down -- towards the center of the Earth.

2. Friction: The force of friction is always parallel to the surface and points (acts)

opposite the direction of movement.

3. Propulsion: This force acts in the direction of movement, parallel to the surface.

It must be at least as strong as the force of friction (otherwise there would be no movement).

In this case it is stronger than friction because it causes acceleration.

B) There are three forces.

1. Gravity: Again it points downward.

Gravity has two effects:

1.1 It presses against the surface causing friction.

1.2 It tries to slide the block down the incline.

These two effects are represented by two forces, whose vector sum MUST be equal the force of gravity.

1.1 is caused by a force perpendicular to the surface, pointing into the surface

1.2 is caused by a force parallel to the surface pointing down along the surface

2. Friction: Again the force of friction is parallel to the surface, and

points opposite the direction of movement.

3. Propulsion: This force acts in the direction of movement, parallel to the surface.

Its size is the sum of the force of friction plus the force 1.2.

It cannot be smaller, because otherwise the box would not move upwards.

It cannot be larger because we are told the box has no acceleration.