Calculating total energy

Question

I have the question:

"Calculate the total energy of the moving object, when mass = $4$ kg, acceleration due to gravity = $9.81~\text{ms}^{-2}$, height = $10$ m and velocity = $3~\text{ms}^{-1}$"

I know that Total energy = potential energy + kinetic energy. Therefore, Total energy = $mgh + \frac{1}{2} mv^2$. However, the value for gravity is not given and I do not know how to calculate this using the following information given. I also do not know if my method of solving the problem is correct. The final units I get for total energy is [$\text{kg}^2\text{m}^2\text{s}^{-4}$].

The units for energy is $\text{J} = \frac{\text{kg}\cdot \text{m}^2}{\text{s}^2}$ — Winther, Oct 19 '16 at 16:43
The value for the acceleration due to gravity is given: $g=9.81 ; m/s^2$. — mathematics2x2life, Oct 19 '16 at 16:59

score 1 · Accepted Answer · answered Oct 19 '16 at 16:43

1

In the potential energy: $E_P=mgh$, $m$ is the mass, $g$ is the acceleration due to gravity and $h$ is the height. So you know all you need and the units of measure are: $$ [mgh]=kg \cdot \frac{m}{s^2}\cdot m =kg \cdot \left(\frac {m}{s} \right)^2 $$ , the same as for the kinetic energy.

answered Oct 19 '16 at 16:43

Emilio Novati

62,675

I got the answer total energy = 410.4 [kgms^-2] is this correct ? – Dan Oct 19 '16 at 16:53
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The value is correct, but the unit of measure is $kg\cdot m^2/s^2$ that is called joule: https://en.wikipedia.org/wiki/Joule – Emilio Novati Oct 19 '16 at 17:00

Calculating total energy

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