Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A sledge starts from rest and slides down an icy slope at . Treat the ice as smooth. Taking , find
On a slope at angle , split the weight: down the slope and into it, so . Sliding down a rough slope, friction acts up it:
A body at rest starts to slide when .
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. , , , no friction.
Plan. , then the equations of motion.
Step 1. Acceleration. .
Step 2. Time. .
Step 3. Speed. .
Answer: (a) . (b) . (c) .
Check. , and . It agrees.
Watch out. is the part of across the slope. It does not speed the sledge up.
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