Solving Ice's Acceleration Down a Sloped Roof

[runningirl]

Homework Statement

A 1.5 kg chunk of ice slides down a roof sloped at a 60 degree angle with the horizontal.
a)If there is no friction, determine the acceleration of the ice.
b) If the force of the friciton is 3.0 N, what is the acceleration of the ice?

Homework Equations

f=ma

The Attempt at a Solution

for part a:
9.8*1.8*sin(60)=12.73 N
12.73/1.5=8.48 m/s/s

part b?!

 

[collinsmark]

part b?!

Have you tried Newton's second law of motion? (Hint: Make sure you find the net force, since there are multiple forces involved.)

 

[runningirl]

Have you tried Newton's second law of motion? (Hint: Make sure you find the net force, since there are multiple forces involved.)

3+F(cos60)?
i don't know the force being pushed on the slope to find the horizontal force ...

 

[collinsmark]

3+F(cos60)?
i don't know the force being pushed on the slope to find the horizontal force ...

Try drawing a block diagram. It will (as always) guide you to setting up the equation(s) correctly. How does mg fit into all of this?

[Edit: And feel free to refer back on your work for part a). It may bring you some insight.]

 

[Paulie323]

Start by drawing a free body diagram this will help you to see what forces are acting and which way(you are going to break the force of mg into components). Afterwards, you can now use this diagram to see what forces are equal,or cancel each other out, and in your case which is greater than the other(force to overcome the friction force). Then use similar techniques as in part a) to aid you in getting your answer.

 

[Yoriko]

Force by gravity in direction of slope = 9.81*1.5*sin60
Net force = 9.81*1.5*sin60 - 3.0

Net force = ma
a = (Net force)/m