# Free Body Diagram and applied force

• ThePhysicsBoy
In summary: According to the problem statement, is the guy accelerating up the incline, or is he just barely moving at a constant speed?The guy is barely moving up the incline, so he is not accelerating.
ThePhysicsBoy

## Homework Statement

A cavewoman is dragging her 65.4 kg mate home, up a gentle 10° incline. The co efficient of friction for skin on oil is 0.40. What is the minimum applied force she needs to keep the neanderthal moving with uniform motion?

ff=μFn
fg=mg
fnet=ma

## The Attempt at a Solution

I tried solving for Ff using ff=μFn but I don't have the Fn do I? We have gravity going down which is -9.8(65.4)=640.92...would that be the force of normal?

f=ma
I have mass but not acceleration? How would i calculate it?

so...fa=65.4(0)...?

it does not..thats my problem :S

:/ Are you sure lol? I am pretty sure he prof wouldn't give a question that's not solveable

ah alright, so prof musta made a mistake. Thanks, Got an exam tommorow though :P hope he doesn't put this question on it

school in Calgary :P

The professor didn't make a mistake.

You already calculated the force of gravity acting on the guy. For a slope of 10 degrees, what are the components of this force in the directions perpendicular and parallel to the incline? What direction does the force parallel to the incline point (up the incline, or down the incline)? If she is trying to pull the guy up the incline, what frictional force does she have to overcome? Make a list of the forces acting on the guy parallel to the incline. How many forces are there? According to the problem statement, is the guy accelerating up the incline, or is he just barely moving at a constant speed?

Chet

- Frictional Force, Moving towards the left
- Force applied going [E 10 N]
- Force of Gravity Down
- Force of Normal Up

Since it says gently, I assume it is moving at a constant velocity? or close to?

What is the next step after Force of gravity?

The gravitational force acting on the guy can be resolved into two components, one perpendicular to the incline and the other parallel to the incline. What are the numerical values of these two components?

component y = -9.7?
Component x = Force of friction ? That is the only force acting in the x direction isn't it?

I can't figure it out :/

ThePhysicsBoy said:
component y = -9.7?
Component x = Force of friction ? That is the only force acting in the x direction isn't it?
What do you mean by "the x direction"? If that is along the surface of the incline, then there is a force in addition to friction acting in the x direction, namely gravity. Gravity has a component along the incline.

ThePhysicsBoy said:
component y = -9.7?
Component x = Force of friction ? That is the only force acting in the x direction isn't it?

You already said that the gravitational force acting on the guy is 641 N. Do you know how to resolve this force into components perpendicular and parallel to the 10 degree incline?

Gravity doesn't exert any frictional force on the guy. The frictional force is exerted on the guy by the inclined plane. But we will get to that later.

## What is a free body diagram?

A free body diagram is a visual representation of the forces acting on an object. It shows all the external forces acting on the object without any consideration for its surroundings or the forces it exerts on other objects.

## How do you draw a free body diagram?

To draw a free body diagram, you first need to identify the object you want to analyze and all the external forces acting on it. Then, draw a simple sketch of the object, labeling it with the known forces acting on it. Finally, draw arrows to represent the direction and magnitude of each force.

## What is the purpose of a free body diagram?

The purpose of a free body diagram is to simplify a complex situation by breaking it down into its individual forces. This makes it easier to analyze the motion of an object and determine the net force acting on it.

## What is an applied force?

An applied force is any external force that is exerted on an object. It can come from various sources, such as a person pushing or pulling an object, or the force of gravity acting on an object.

## How do you calculate the net force on an object?

To calculate the net force on an object, you need to add up all the individual forces acting on the object. If the net force is zero, the object will remain at rest or continue moving at a constant velocity. If the net force is non-zero, the object will accelerate in the direction of the net force.

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