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### Work and Energy Problem

```
Date: 5/14/96 at 17:10:1
From: Anonymous
Subject: Work and Energy Problem

I am a junior in a senior Math Analysis class in High School.  We are
working on Work and Energy problems in Integral Calculus. However, our
teacher told us not to use calculus for these problems. Instead we
should use the formula:

Work = |F||d|cosO (theta)
where theta is the angle betwee F and d.

I'm having a problem trying to figure out exactly how to do this.  I
can't seem to find what angle I should use or what to plug in where.

Question:
The mass of a loaded helicopter is 1500kg.  How much energy does
its engine expend in ascending vertically for 120m?

Thanks a lot.
```

```
Date: 11/12/96 at 21:46:24
From: Doctor Robert
Subject: Re: Work and Energy Problem

In this case the angle between the force vector and the displacement
vector is zero degrees.  The cosine of zero is 1 so the formula
becomes:

W = F times d

= 1500 kg times 9.8 nt/kg times 120 m = 1.764 x 10^6 joules

In a different type of problem, one might have the displacement vector
in a different direction from the force vector.  A simple example of
this is pulling a box along the floor by attaching a rope to it so
that the rope makes an angle of 60 degrees above the horizontal. In
this case the displacement is horizontal, but the force is not.

-Doctor Robert,  The Math Forum
Check out our web site!  http://mathforum.org/dr.math/
```
Associated Topics:
High School Physics/Chemistry

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