A box with an initial speed of 1ms is moving up a ramp. The ramp has a kinetic friction coefficient of 34 and an incline of π8. How far along the ramp will the box go?

2 Answers
Mar 4, 2018

The distance is =0.05m

Explanation:

Resolving in the direction up and parallel to the plane as positive +

The coefficient of kinetic friction is μk=FrN

Then the net force on the object is

F=FrWsinθ

=Frmgsinθ

=μkNmgsinθ

=mμkgcosθmgsinθ

According to Newton's Second Law of Motion

F=ma

Where a is the acceleration of the box

So

ma=μkgcosθmgsinθ

a=g(μkcosθ+sinθ)

The coefficient of kinetic friction is μk=34

The acceleration due to gravity is g=9.8ms2

The incline of the ramp is θ=18π

The acceleration is a=9.8(34cos(18π)+sin(18π))

=10.54ms2

The negative sign indicates a deceleration

Apply the equation of motion

v2=u2+2as

The initial velocity is u=1ms1

The final velocity is v=0

The acceleration is a=10.54ms2

The distance is s=v2u22a

=01210.54

=0.05m

Mar 4, 2018

Here,downward component of the weight of the box which tries to pull it down along the plane is mgsin(π8)=0.383mg

And,maximum value of kinetic frictional force that can act is μ×N=34mgcos(π8)=0.693mg

Now, initially,the box has a tendency to go up,so frictional force will act along with the downward component of its weight to stop the motion.

So,net acceleration downwards will be 1.076g

So,if it goes up by xm,we can say,02=122×1.076gx

Or,x=0.05m

After that the block will come to momentary rest and try to move down due to its downwards component of weight,but maximum frictional force value is more than that,so it will keep the block at rest at that point.