Question

A man of mass 60 kg is standing on a horizontal conveyor belt. When the belt is given an acceleration of $2m{s}^{-2}$, the man slides back on the belt with an acceleration $1m/s^2$, with respect to the belt. If $g=10m{s}^{-2}$, the net force (in Newton) acting on the man will be :

• A. $60$
• B. $90$
• C. $30$
• D. $120$

Answer 1

The correct option is A $60$

Since acceleration of belt with respect to ground is $2m/s^2$
and acceleration of man w.r.t belt is $1m/s^2$
therefore acceleration of man w.r.t ground will be
$a_{mg}=a_{bg}-a_{mb}$
where, $a_{mg}$ is acceleration of man w.r.t ground
$a_{bg}$ is acceleration of belt w.r.t ground
$a_{mb}$ is acceleration of man w.r.t belt
$a_{mg}=2-1=1m/s^2$
Therefore, net force acting on man will be
$F_{net}=mass\times a_{mg}$
$F_{net}=60\times 1$
$F_{net}=60N$
option (A) is correct