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1. Students in a physics class placed two objects on the top of a ramp as shown

ID: 1873127 • Letter: 1

Question

1. Students in a physics class placed two objects on the top of a ramp as shown in the diagrams above. The ramp has a small rise at the end which causes objects to be launched upwards at a small angle. First the students placed a block of ice (which has no friction with the ramp’s surface) at the top of the ramp and released it. Next, the students placed a thin hoop at the top of the ramp and released it.

a) Which of the two objects, if either, reaches a greater height after leaving the ramp? Justify your answer qualitatively without any equations.

b) Which, if either, would reach a greater height if the hoop was also made of ice and slid down the ramp without rolling? Justify your answer qualitatively without any equations.

c) Suppose the final angle of the ramp is 30º. How can the maximum height of each be determined?

Africtionless block of ice with m ass, m slides down the ramp from rest. ML A thin hoop m ass, m, andra dius,r, rolls down the rampfrom rest without slipping

Explanation / Answer

a. in the given figures, both the objects have the same mass and are released from the same initial height

but when they come down even though they have lost the same anount of PE, the have not gained the same ampount of translational KE

The ice block on one hand has all its PE concerted to Translational KE

the rolling hoop has its PE divided into Tranlational KE and rotational KE

hence

the rolling hoop has less linear speed at the enfd of the incline and the ice block reaches greater height after jumping off from the end of the incline

b. if the hoop slid down, and did not rotate, then it will too reach the same height as the ice block

c. angle of ramp = theta

hence

final height = h

initial height = H

from conservation of energy

mgH = 0.5mv^2*cos^2(30) + mgh

and mgH = 0.5mv^2

hecne

mgH = mgH*cos^2(30) + mgh

h = mgH*sin^2(30) = mgH/4