Solve for Pulling Force for Sled w/ Mass, Angle, & Coeff. of Friction

In summary, to move the sled from rest, a force of at least 24.0 kg is needed, and the angle at which the father applies the force must be 26.0°.
  • #1
nina123
5
0

Homework Statement



A father gives his daughter a ride on a sled by applying a force F at an angle θ = 26.0° with respect to the horizontal. If the coefficient of static friction is µs = 0.153, and the combined mass of sled and child is m = 24.0 kg
What is the minimum amount of force required to move the sled from rest by
pulling it

Homework Equations



F=ma

The Attempt at a Solution



I have tried multiple ways and i keep getting the wrong answer,
I think i should take the sum of all the forces in the x direction and of the y direction and somehow get the force i need but I am not exactly sure.

HELP PLEASE?
 
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  • #2


The words "minimum amount of force" and "from rest" imply that this is a statics problem. In statics, what is the special condition on the net force? What does the word "static" imply about the value of the acceleration in f=ma?
Once you figure that out, you should have your net x force components (which requires trig) sum to this special value for the net force as well as you net y force components (which also requires trig).
EDIT: Also make sure you have your pulling force in the correct direction. Did you draw a free body diagram?
 
  • #3


runningninja said:
The words "minimum amount of force" and "from rest" imply that this is a statics problem. In statics, what is the special condition on the net force? What does the word "static" imply about the value of the acceleration in f=ma?
Once you figure that out, you should have your net x force components (which requires trig) sum to this special value for the net force as well as you net y force components (which also requires trig).

So "static" would imply that the value of acceleration =0 ?right?

so i have in the x direction:
F(pull,x) + F(friction,x) +W(x) + n(x) = 0
but there is no W or F(gravity) in the x direction so that equals zero and same for n(x) (normal force) =0.
therefore i have:
F(pull,x) +f(friction,x)=0 right?

In the y direction:
F(pull,y) + F(friction,y) +W(y) + n(y) = 0
F(friction,y)=0
therefore i have:
F(pull,y) +W(y) + n(y) = 0 right?

then F(pull,x) = F(pull)cosθ
and F(pull,y) =F(pull)sinθ

I all that I've said is correct now, what would i do now? or is there other things that i am missing ?
 
  • #4


Since the force is pulling, is your pulling force positive or negative? Is your weight positive or negative?
I see two equations and two unknowns (Fpull and normal). Pull out your algebra toolkit and solve it.
 
  • #5


thanks for your help, i got the answer :P
 

1. What is the formula for calculating the pulling force for a sled?

The formula for calculating the pulling force for a sled is F = (mgsinθ + μmgcosθ), where F is the pulling force, m is the mass of the sled, g is the acceleration due to gravity, θ is the angle of the incline, and μ is the coefficient of friction.

2. How does the angle of the incline affect the pulling force?

The angle of the incline affects the pulling force because as the angle increases, the component of gravity pulling the sled down the incline also increases. This results in a greater pulling force needed to overcome the force of gravity and the friction between the sled and the surface.

3. What is the significance of the coefficient of friction in this calculation?

The coefficient of friction is a measure of the resistance between two surfaces in contact. In this calculation, it represents the resistance between the sled and the surface it is being pulled on. A higher coefficient of friction means a greater pulling force is needed to overcome this resistance.

4. How does the mass of the sled impact the pulling force?

The mass of the sled directly affects the pulling force needed. A heavier sled will require a greater pulling force to overcome the force of gravity and the resistance caused by friction. This is because the force of gravity is directly proportional to the mass of the object.

5. Can this formula be applied to other objects besides sleds?

Yes, this formula can be applied to any object being pulled on an incline with a known mass, angle, and coefficient of friction. It is commonly used in physics and engineering to calculate the necessary pulling force for various scenarios.

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