You pull on a rope that is attached to a box. The rope makes an angle of 25 degrees with the ground. You are pulling the box at a constant velocity. The force you are pulling with is 78N. The box weighs 25N. You pull the box a displacement of +16m.
What is the work done by you?
I got 7.25
What is the work done by friction?
What is the work done by the normal force?
I got 0
What is the work done by gravity?
can someone help me get the rest of this
How did you get 7.25? What are the dimensions of that number?
The answer is not 7.25 Joules. Multiply the horizontal force component by the distance the block moves. That is how to compute the work done.
The work done by friction is MINUS the work done by the person pulling.
The normal force and gravity do no work, since there is no motion in the vertical direction
To calculate the work done by you, we use the formula:
Work = Force × Displacement × Cos(θ)
where:
- Work is the work done (in joules)
- Force is the applied force (in newtons)
- Displacement is the distance the box is pulled (in meters)
- θ is the angle between the force and the displacement
Using the given values:
Force = 78N
Displacement = +16m
θ = 25 degrees
Plugging these values into the formula:
Work = 78N × 16m × Cos(25°)
Work = 1248N · m · Cos(25°)
Work ≈ 1110.4 joules
So, the work done by you is approximately 1110.4 joules.
Now let's calculate the work done by friction. Since the box is moving at a constant velocity, it means that the force of friction is equal and opposite to your applied force. Therefore, the work done by friction is:
Work = - Force × Displacement
Using the given values:
Force = 78N
Displacement = +16m
Plugging these values into the formula:
Work = - 78N × 16m
Work = - 1248N · m
Work = - 1248 joules
So, the work done by friction is -1248 joules.
Next, let's calculate the work done by gravity. The work done by gravity is the product of the gravitational force and the vertical displacement. Since the box is moved horizontally, the vertical displacement is zero, and therefore the work done by gravity is also zero.
Finally, to calculate the work done by the normal force, we need to consider that the normal force acts perpendicular to the displacement. Since the box is moving horizontally, the normal force does no work. Therefore, the work done by the normal force is zero.
To summarize:
- The work done by you is approximately 1110.4 joules.
- The work done by friction is -1248 joules.
- The work done by gravity is zero.
- The work done by the normal force is zero.