Calculate the average force used to drag a box up a ramp

In summary: The direction of the force is not stated, but it is assumed to be in the downward direction because the box was initially at the bottom of the ramp.The direction of the force is not stated, but it is assumed to be in the downward direction because the box was initially at the bottom of the ramp.
  • #1
RyanRhino
3
0
Homework Statement
A 150. kg box is dragged up a 4.00 m long ramp inclined at 20.0 degrees to the horizontal. You are told that the efficiency of the ramp is 55.0%
a) find the average force that is used to drag the box up the ramp.
Relevant Equations
W = (FacosX)(d)
%Eff. = Eout/Ein x 100%
I first wrote down that 55% = Eout/Ein
I also know that W = (Facos20)(4)
and I substitute it into the first equation
55% = Eout/[(Facos20)(4)]
But I'm missing two variables here. Did i forget something or is the question missing some information?
 
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  • #2
RyanRhino said:
W = (Facos20)(4)
How are you defining F there (or is it Fa?)? I ask because I am unsure how you arrive at cos.
Would that W be Ein or Eout?
What information have you not used?

Apart from all that, the question is wrong in asking for the average force. With the given information, you can only solve it by assuming the force is constant.
 
  • #3
haruspex said:
How are you defining F there (or is it Fa?)? I ask because I am unsure how you arrive at cos.
Would that W be Ein or Eout?
What information have you not used?

Apart from all that, the question is wrong in asking for the average force. With the given information, you can only solve it by assuming the force is constant.
So F there i believe is Fa and that W would be the total work put in which would be Ein
 
  • #4
RyanRhino said:
So F there i believe is Fa and that W would be the total work put in which would be Ein
You have not explained how you get the cos(20) in there.
What direction are you supposing the force to be in? In what direction is the length measured?

How can you calculate Eout? What was achieved by dragging the box up?
 
  • #5
haruspex said:
You have not explained how you get the cos(20) in there.
What direction are you supposing the force to be in? In what direction is the length measured?

How can you calculate Eout? What was achieved by dragging the box up?
Sorry i forgot, the cos 20 is from the ramp of how it is 20 degrees above the horizontal we just pushed the box up the ramp
 
  • #6
RyanRhino said:
Sorry i forgot, the cos 20 is from the ramp of how it is 20 degrees above the horizontal we just pushed the box up the ramp
That is not what I meant. I know the ramp is at 20 degrees, but what is your reasoning for including the cosine of it in that expression?

Try to answer my questions:
What direction are you supposing the force to be in?
In what direction is the length measured?
 

1. How do you calculate the average force used to drag a box up a ramp?

The average force used to drag a box up a ramp can be calculated by dividing the weight of the box by the distance it is dragged up the ramp. This is known as the work-energy theorem, which states that the work done on an object is equal to the force applied multiplied by the distance it is moved.

2. What is the weight of the box?

The weight of the box is the force of gravity acting on the box. It can be calculated by multiplying the mass of the box by the acceleration due to gravity, which is typically 9.8 meters per second squared.

3. How do you calculate the distance the box is dragged up the ramp?

The distance the box is dragged up the ramp can be calculated by using the Pythagorean theorem. This theorem states that the square of the hypotenuse (the distance up the ramp) is equal to the sum of the squares of the other two sides (the horizontal distance and the vertical height of the ramp).

4. What is the significance of calculating the average force used to drag a box up a ramp?

Calculating the average force used to drag a box up a ramp can help us understand the amount of work being done and the effort required to move the box. It can also be used to optimize the ramp angle and the amount of force needed to minimize the effort required to move the box.

5. What factors can affect the average force used to drag a box up a ramp?

The average force used to drag a box up a ramp can be affected by the weight of the box, the angle of the ramp, the friction between the box and the ramp, and any external forces acting on the box. Additionally, the surface of the ramp and the smoothness of the box can also impact the average force needed.

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