# What is the work that he does on his body?

• alaa amed
In summary: Ok, now please post your working.In summary, man exerts a force of 510 N on a crate and moves it up a 17.5° ramp with a constant speed. He does work on the crate and on his own body to get up the ramp.

## Homework Statement

A 75-kg man pushes a crate 4.5 m up along a ramp that makes an angle of 17.5° with the horizontal. He exerts a force of 510 N on the crate parallel to the ramp and moves it at a constant speed.

Calculate the work done by man to move the crate, in joules. Be sure to include the work he does on the crate and on his body to get up the ramp.

2. Homework Equations

W = F cos theta d

## The Attempt at a Solution

I calculated the work that he does on the box using that above equation but could not figure out what the secind part of the question is getting at[/B]

Work done by the man(against gravity) would be equal to the change(increase) in his potential energy.

cnh1995 said:
Work done by the man(against gravity) would be equal to the change(increase) in his potential energy.
I'm sure that is the intent of the question, but strictly speaking he does no work on the crate or on his own body. Work done on a rigid object equates to the gain in its KE, which is zero here. The work done by the man consists of work done on the objects (zero) plus the work done on the gravitational system consisting of those objects and the Earth.

haruspex said:
I'm sure that is the intent of the question, but strictly speaking he does no work on the crate or on his own body. Work done on a rigid object equates to the gain in its KE, which is zero here. The work done by the man consists of work done on the objects (zero) plus the work done on the gravitational system consisting of those objects and the Earth.
True, the net work done on the crate is zero. However, that consists of the man doing (positive) work on the crate and gravity doing (negative) work on the crate.

SammyS said:
True, the net work done on the crate is zero. However, that consists of the man doing (positive) work on the crate and gravity doing (negative) work on the crate.
Doesn't seem any more reasonable as a way to view it, but if you wish to go that path you'd have to say the man does some work on the crate and some on the Earth, with gravity doing negative work on both.

haruspex said:
Doesn't seem any more reasonable as a way to view it, but if you wish to go that path you'd have to say the man does some work on the crate and some on the Earth, with gravity doing negative work on both.
The work that the man does on the Earth is essentially zero.

I do agree that the issue of what work the man does on himself is problematical.

Last edited:
cnh1995 said:
Work done by the man(against gravity) would be equal to the change(increase) in his potential energy.
If the man's potential energy is added to the work he does on the crate, it does not yield the right answer which in this case is 3.14x10^3 J.

alaa amed said:
W = F cos theta d
In that equation, what is the necessary geometric relationship between F, d and theta in the physical arrangement?

haruspex said:
In that equation, what is the necessary geometric relationship between F, d and theta in the physical arrangement?
F is the magnitude of the force acting on the system.
d is the magnitude of the displacement of the system.
and theta is the angle between the force vector and the displacement vector?

alaa amed said:
F is the magnitude of the force acting on the system.
d is the magnitude of the displacement of the system.
and theta is the angle between the force vector and the displacement vector?
(I get nearly 3300J.)

## What is the purpose of doing work on his body?

The purpose of doing work on one's body is to improve physical fitness, strength, and overall health. This can include activities such as exercise, proper nutrition, and rest.

## What are some examples of work that can be done on the body?

Examples of work that can be done on the body include weightlifting, cardio exercises, stretching, and proper nutrition habits. It can also involve activities such as massage, skincare, and grooming.

## Can doing work on the body have any negative effects?

Yes, doing excessive or improper work on the body can have negative effects such as injuries, fatigue, and stress. It is important to listen to your body and consult a professional before starting any new regimen.

## Is it necessary to do work on the body?

It is not necessary for everyone to do work on their body, but it is generally recommended for maintaining good overall health and preventing certain health conditions. However, the specific type and amount of work may vary for each individual.

## How often should one do work on their body?

The frequency of doing work on the body depends on individual goals and needs. Generally, it is recommended to engage in physical activity at least 3-4 times a week for optimal health benefits. However, it is important to listen to your body and make adjustments as needed.