Ice chunk sliding down a 60° roof without friction

[runningirl]

Homework Statement

A 1.5 kg chunk of ice slides down a roof sloped at a 60 degree angle with the horizontal.

a) Find the acceleration given that there is no friction.

b) Show that the amount of mass doesn't matter in part a.

Homework Equations

f=ma

The Attempt at a Solution

9.8*1.5(sin60)=fg

a= f/m
a=12.73/1.5
a=8.49 m/s/s.

i couldn't get part b?!

 

[homevolend]

Mass doesn't matter because there is no friction to stop it from sliding. So it could be any mass and continue to slide.

 

[Kreamer]

Since force friction is 0 and force normal cancels with the force going into the ramp, the force going down the ramp is your Fnet.

Fnet = mgsin(60)
ma = m(9.8)sin(60)
mass on each side cancels out.
a = (9.8)sin(60)
a = 8.49