A box with an initial speed of 8ms is moving up a ramp. The ramp has a kinetic friction coefficient of 23 and an incline of π6. How far along the ramp will the box go?

2 Answers
Jul 20, 2017

The distance is =3.03m

Explanation:

Taking 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

F=ma

Where a is the acceleration

ma=μkgcosθmgsinθ

a=g(μkcosθ+sinθ)

The coefficient of kinetic friction is μk=23

The incline of the ramp is θ=16π

a=9.8(23cos(16π)+sin(16π))

=1056ms2

The negative sign indicates a deceleration

We apply the equation of motion

v2=u2+2as

u=8ms1

v=0

a=11.5ms2

s=v2u22a

=064210.56

=3.03m

Jul 21, 2017

Distance traveled up the ramp = 3.03087 m (after rounding off)

Explanation:

We can apply energy conservation rule here.

Initial K.E. of the box = Final P.E. of the box + energy lost due to friction

This is because initial P.E. of the box is zero as height is zero.
Also final K.E. is zero because box is finally at rest.

Suppose 'm' is the mass of box, 'u' is the initial velocity (8ms), 'h' is the height through which it raises, 's' is the distance traveled along the ramp which is to be calculated.

Initial K.E. = 12mu2
Final P.E. = mgh
Energy lost due to friction = work done to overcome frictional force
= Fks
= μkmgscos(π6)

Put it together to get

12mu2=mgh+μkmgscos(π6)...............(1)

Cancel the common mass from both sides.
From the right angled triangle (that I am not inserting here) we get
h=ssin(π6)

Simplifying the equation (1) we get,
s=3u2g(2+3)

put u = 8 ms, g = 9.8 ms2, so

s=3.03087m