# Help with Newtons laws and friction

• beamerrox
In summary, a girl is skiing down a 35 degree inclined hill that is 120 meters long. She starts from rest and the snow has a coefficient of friction of .12. The equations used in this problem are ΣF=MA, ΣF=9.8(m), vi=0m/s, ΛD=120m, vf=?, t=?, and a=? By taking into account the direction of motion, it is possible to solve for the girl's acceleration and the time it takes her to travel the 120 meters. However, it may not be possible to solve using CAE's and instead, the sine and cosine functions may need to be used.
beamerrox

## Homework Statement

a girl is skiing down a 35 degree inclined hill that is 120 meters long. She starts from rest and the snow has a coefficient of friction of .12.
A. Draw an FBD
B what is her acceleration
c. How much time dows it take her to travel the 120 meters

## Homework Equations

I am unsure on how to set up the question solution. I think it's CAE's that are used as well, but i am completely unsure.

## The Attempt at a Solution

ΣF= MA
ΣF=9.8(m)
vi= 0m/s
ΛD=120 m
vf = ?
t=?
a=?
120cos35= 98.29?
120sin35= 68.82?

If anyone could please help i would really appreciate it. If i can figure out how to set this problem up and solve it, i will be able to figure the other problems out. Thank you so much!
I don't think there's enough to solve it using cae's can i use the sin and cosine functions with the 35 degrees??

You have to take her direction of motion into consideration. If you've drawn a FBD you see that there's a difference in the direction of the forces that have an effect on her acceleration. If you can take this into consideration?

Hello! I would be happy to assist you with understanding Newton's laws and friction. Let's start by drawing a free body diagram (FBD) for the girl skiing down the hill. An FBD is a visual representation of all the forces acting on an object. In this case, the object is the girl.

A. FBD:
The girl is represented as a dot in the middle of the diagram. The forces acting on her are the gravitational force (Fg), the normal force (Fn), and the frictional force (Ff). The gravitational force is pointing straight down, the normal force is perpendicular to the surface of the hill, and the frictional force is pointing up the hill.

B. Acceleration:
To find the girl's acceleration, we can use Newton's second law, which states that the net force acting on an object is equal to its mass multiplied by its acceleration (ΣF=MA). Since we know the mass of the girl (let's say it's 50 kg), we can solve for the acceleration by dividing the net force by her mass.

To find the net force, we need to first find the components of the gravitational force and the frictional force. We can use trigonometry to do this. The component of the gravitational force acting down the hill is Fgcos35, and the component acting perpendicular to the hill is Fgsin35. The frictional force is equal to the coefficient of friction (μ) multiplied by the normal force (Fn).

So our equation for the net force is:
ΣF = Fgcos35 - μFn

Substituting in the values we know, we get:
ΣF = (50 kg)(9.8 m/s^2)cos35 - (0.12)(Fn)

To find the normal force, we can use Newton's third law, which states that for every action, there is an equal and opposite reaction. In this case, the normal force is equal to the component of the gravitational force perpendicular to the hill, or Fgsin35.

So our equation for the normal force is:
Fn = Fgsin35

Substituting in the values we know, we get:
Fn = (50 kg)(9.8 m/s^2)sin35

Now we can substitute this value into our equation for the net force:
Σ

## 1. What are Newton's laws of motion?

Newton's laws of motion are three physical laws that describe the relationship between an object's motion and the forces acting upon it. The first law states that an object at rest will stay at rest and an object in motion will stay in motion with a constant velocity unless acted upon by an external force. The second law explains how the acceleration of an object depends on the mass of the object and the net force acting on it. The third law states that for every action, there is an equal and opposite reaction.

## 2. How does friction affect an object's motion?

Friction is a force that opposes the motion of an object. It acts in the opposite direction of an object's motion and can slow down or stop the object's motion. Friction is caused by the roughness of surfaces and is dependent on the weight of the object and the type of surface it is moving on. In some cases, friction can be beneficial, such as in the case of car brakes, where it helps to slow down the vehicle.

## 3. What factors affect the amount of friction between two surfaces?

The amount of friction between two surfaces is affected by several factors, including the roughness of the surfaces, the force pressing the surfaces together, and the type of material the surfaces are made of. Rougher surfaces and higher forces will result in greater friction, while smoother surfaces and lower forces will result in less friction. The type of material also plays a role, as some materials have a higher coefficient of friction than others.

## 4. How can we reduce friction between two surfaces?

There are several ways to reduce friction between two surfaces. One way is by lubrication, which involves adding a substance between the two surfaces to reduce the contact between them and make them slide more easily. Another way is by using smoother surfaces, such as using ball bearings to reduce friction in a machine. Additionally, reducing the force pressing the surfaces together can also decrease friction.

## 5. How do Newton's laws apply to everyday situations?

Newton's laws of motion apply to everyday situations in many ways. For example, the first law explains why objects stay at rest unless a force is applied to them, which is why a book will stay on a table unless someone picks it up. The second law can be seen in the relationship between force, mass, and acceleration, such as when pushing a shopping cart that has a heavier load. The third law can be observed in actions like jumping, where the force of pushing down on the ground causes an equal and opposite force that propels us upwards.

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