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 the rocket's mechanical energy when it takes off?

Answer 1

I found `16kJ`

Explanation:

We can choose the firing position as "zero" for Gravitation Potential Energy (height `h` zero);
Mechanical energy at this point will be given as the contribution of Potential and Kinetic energy:
`E_("mec")=U+K=mgh+1/2mv^2`
but `U=0` and so:
`E_("mec")=0+K=K=1/2mv^2=1/2(2.7)(110)^2=16,335J~~16kJ`