There are three forces $\vec {F_1}$, $\vec {F_2}$ and $\vec {F_3}$ acting on a body, all acting on a point $P$ on the body. The body is found to move with uniform speed.
$(a)$ Show that the forces are coplanar.
$(b)$ Show that the torque acting on the body about any point due to these three forces is zero.
As shown in figure, three forces $\mathrm{F}_{1}, \mathrm{~F}_{2}, \mathrm{~F}_{3}$ act at point $\mathrm{P}$ on body.
$(a)$ Figure shows that forces are in same plane that is forces are coplaner. Body moves with constant uniform speed (velocity).
$\therefore a =0$
$\mathrm{~F} =m a$
$=m(c)$
$=0$
$\therefore \overrightarrow{\mathrm{F}}_{1} +\overrightarrow{\mathrm{F}}_{2}+\overrightarrow{\mathrm{F}}_{3}=0$
$(b)$ Calculating torque of these forces about point$ P$. As forces passes through$ P$ torque about point $\mathrm{P}$ is zero.
What is dynamics ?
A parachutist with total weight $75 \,kg$ drops vertically onto a sandy ground with a speed of $2 \,ms ^{-1}$ and comes to halt over a distance of $0.25 \,m$. The average force from the ground on her is close to ............ $N$
What are concurrent forces ? Explain equilibrium of particle under effect of concurrent forces.
Block $A$ of mass $4 \;kg$ is to be kept at rest against a smooth vertical wall by applying a force $F$ as shown in figure. The force required is .......... $N$ $\left(g=10 m / s ^2\right)$
Write important guidance for solving problems in mechanics.