Question

A model rocket with a mass of 2.7kg is launched straight up from the ground at a speed of 110m/s. What is its mechanical energy at the maximum height?

Answer 1

I found: `16335J`

Explanation:

At maximum height velocity will be zero so Kinetic Energy will also be zero. Mechanical Energy will be given entirely by Gravitational Potential Energy `U=mgh`.

To find `h` we use the relationship:

`v_f^2=v_i^2+2ah`

where:
`v_f=` final velocity`=0`;
`v_i=` initial velocity `=110m/s`;
`a=-g` acceleration of gravity `=-9.8m/s^2` negative because directed downwards;

So:
`110^2=0^2-2*9.8h`
`h=617m`
And:
`U=2.7*9.8*617=16335J~~16KJ`