Mechanical work
The mechanical work W (scalar value) is found by the formula:
W = $\overrightarrow{F}$·$\overrightarrow{r}$·cosΘ
$\overrightarrow{F}$ — force, N;
$\overrightarrow{r}$ — movement, m.
when Θ=900, W=0.
Mechanical work is measured in Joules (J).
The concept of mechanical work is closely related to the scalar product of two vectors.
Mechanical power
The mechanical power P (scalar physical quantity) is found by the formula:
$P=\frac{W}{t}$
t-time, s.
Mechanical power is measured in Watts (W).
Example
A person pulls the sled by applying a force $\overrightarrow{F}$=1000 N at an angle α=30° to the horizon. Under this force, the sled moves horizontally at a speed of $\overrightarrow{v}$=5 m/s. Find the power P of the force $\overrightarrow{F}$.
Solution
$P=\frac{\overrightarrow{F}\overrightarrow{r}cosα}{t}=FVcosα$
$P=1000N\cdot5m/s\cdot\cos30\approx4330,127$
571