A crate of mass m is gently placed with zero initial velocity on an inextensible conveyor belt that is moving to the right at a constant speed v0. Treating the crate as a particle and assuming that the coefficients of static and kinetic friction between the crate and conveyor are μs and μk, respectively, determine:
(a) the distance the crate slides before it stops slipping relative to the belt, and
(b) the time it takes for the crate to stop sliding.
Figure P3.154
Draw the free body diagram of the crate.
Apply the equilibrium equation in the direction.
Here, is the mass of the crate, and
is the normal force.
Apply the Newton’s second law equation in the direction.
Here, is the acceleration, and
is the frictional force.
Apply the friction law for slip, assuming that.
Substitute for
.
Here, is the coefficient of kinetic friction between the crate and conveyor.
Substitute for
.
(a)
Calculate the distance the crate slides before it stops by assuming constant acceleration.
Here, is the initial velocity,
is the final velocity.
Substitute for
,
for
and 0 for
.
Therefore, the distance the crate slides before it stops slipping is.
(b)
Calculate the stopping time.
Substitute for
,
for
and 0 for
.
Therefore, the time it takes for the crate to stop is.