Physics — Net work on a box being pulled…

[Arsana]

Homework Statement

How to calculate the net work

Homework Equations

A 5 kg box is pulled with a force F = 100 N for 5 m long inclined plane. The height of the inclined plane is 4 m and angle of inclination is 53^

a) What is a work done by force F?

b) What is the work done normal force N?

c) What is the work done by gravitational force ?

d) What is the net work done on the box?

The Attempt at a Solution

First I tried to find a) one. I multiplied 100 * 5 * cos(53) = 300,90
2) N = mg cos(53) ; N = 5 * 10 * cos (53) = 30.090
3) Wg = -mg h
Wg = -200
4) ...?
I found all of the formulas in internet and now I am confused, because it seems like I have done nothing right. If you know that, answer me, please!

 

[haruspex]

I multiplied 100 * 5 * cos(53)

What direction is the applied force in?

2) N = mg cos(53) ; N = 5 * 10 * cos (53) = 30.090

That's the normal force, but the question asks for the work done by it. How do you calculate the work done by a force?

 

[Arsana]

direction

There is nothing about direction on the picture

 

[Arsana]

work done by a force?

Work = Mass * Gravity * Height

 

[haruspex]

Wg = -200

With g=10m/s², that is correct.

 

[haruspex]

There is nothing about direction on the picture

You have a picture? Can't you tell the direction from that? Basically, is the force horizontal or parallel to the slope?

Work = Mass * Gravity * Height

That's for the work done by gravity. What about a force in general?

 

[ZapperZ]

Homework Statement

How to calculate the net work

Homework Equations

A 5 kg box is pulled with a force F = 100 N for 5 m long inclined plane. The height of the inclined plane is 4 m and angle of inclination is 53^

a) What is a work done by force F?

b) What is the work done normal force N?

c) What is the work done by gravitational force ?

d) What is the net work done on the box?

The Attempt at a Solution

First I tried to find a) one. I multiplied 100 * 5 * cos(53) = 300,90
2) N = mg cos(53) ; N = 5 * 10 * cos (53) = 30.090
3) Wg = -mg h
Wg = -200
4) ...?
I found all of the formulas in internet and now I am confused, because it seems like I have done nothing right. If you know that, answer me, please!

There's a severe problem with the way you attempt to solve this problem. If this is what you are accustomed to, you have not understood anything. What you wrote in your solution are mostly undefined (i.e. what is "N", "W", etc..?).

You define these things (and the directions) by making a free-body diagram! This is a MUST in any problem like this (my students are required to show it and they will not receive full credit if the sketch is missing).

So start in the beginning and draw the free-body diagram!

BTW, why are you hunting through the "internet" for the relevant equations? Don't you come across them in class or in your text?

Zz.