Find the magnitudes of all of the forces acting on the sled

In summary, the conversation discusses a person pulling a 5 kg sled with a rope at an angle of 30 degrees with the horizontal, which accelerates horizontally at 1.7 m/s^2. The problem is approached using the equations Fnet = ma and Fgravity = mg, and the forces involved are Fnorm, Fg, and Fr. Using the x and y components of Fr, the forces are added to find the net force, but they must be added as vectors, not scalars. The conversation ends with a question about how to add vectors, to which the expert responds by saying that the components have already been added.
  • #1
NkaujHelp
16
0

Homework Statement


A person pulls on a rope attached to a 5 kg sled. The rope makes an angle of 30 degrees with the horizontal. Sled accelerates horizontally at 1.7 m/s^2. There is no friction.

Homework Equations


ma = Fnet
mg = Fgravity

The Attempt at a Solution


Fnorm = Earth force up on sled
Fr = the force of the rope of the sled being pulled

The x and y components for Fr would be y = Frsinθ and x=Frcosθ.
Vector of Fnorm = <0, Fnorm>
Vector of Fg = <0, -50>
Vector of Fr = <Frcos30, Frsin30>

Fnetx => 8.5 = Frcos30
Fnety => 0 = Fc - 50 + Frsin30

So I got this far and starting doing algebraic stuff to solve for Fr and then plugging that into the second equation. From there, I solved for Fc, and the value was 45.095 N. And from the Fnetx equation, Fr = 9.8 N.
However, when I added all the magnitudes of forces, my answer does not equal to the Fnet, which is ma = 8.5 N.
Can someone help me with this? Have I forgotten something? Am I even doing this right?
 
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  • #2
Show us how you added up the forces to get the net force. Your answers so far look OK.

Chet
 
  • #3
For the net force, I did the force magnitude of Fnorm plus force magnitude of Fr minus the force magnitude of Fg, which is 8.5 N + 45.095 N - 50 N. That answer got me 3.595 N.
 
  • #4
NkaujHelp said:
For the net force, I did the force magnitude of Fnorm plus force magnitude of Fr minus the force magnitude of Fg, which is 8.5 N + 45.095 N - 50 N. That answer got me 3.595 N.
The forces have to be added as vectors, not as scalars.

Chet
 
  • #5
Chestermiller said:
The forces have to be added as vectors, not as scalars.

Chet

How do I do that?
 
  • #6
NkaujHelp said:
How do I do that?
You do it by adding their components. But, you've already done that.

Chet
 

1. What are the forces acting on the sled?

The forces acting on the sled include the force of gravity, the normal force, and the force of friction.

2. How do I calculate the magnitude of the forces?

The magnitude of the force of gravity can be calculated using the formula F = mg, where m is the mass of the sled and g is the acceleration due to gravity. The magnitude of the normal force can be calculated by multiplying the weight of the sled by the cosine of the angle of the slope. The magnitude of the force of friction can be calculated using the formula F = μN, where μ is the coefficient of friction and N is the normal force.

3. Can you explain the concept of vector addition in relation to finding the magnitudes of forces on the sled?

In order to find the net force on the sled, we must use vector addition to determine the magnitude and direction of each individual force acting on the sled. This involves adding the x-components and y-components of each force using the Pythagorean theorem and trigonometric functions.

4. How does the slope of the surface affect the magnitudes of the forces on the sled?

If the surface is inclined, the force of gravity will have a component that is parallel to the slope, which will increase the magnitude of the force of friction. The normal force will also be affected, as it will have a smaller magnitude compared to a flat surface.

5. Are there any other factors that may affect the magnitudes of the forces on the sled?

Yes, other factors that may affect the magnitudes of forces include the mass of the sled, the type of surface the sled is on, and any external forces acting on the sled. Additionally, the magnitude of the normal force may be affected if the sled is accelerating or decelerating.

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