Lecture 3 - Ramps, Newton's 3rd Law, and Energy

Question 1

Why doesn’t a piano fall through a sidewalk?

Answer 1

The sidewalk pushes up on it and supports it.

Question 2

Can a sidewalk and a piano occupy the same space? Why?

Answer 2

No, the sidewalk exerts a “support force” on the piano that prevents it from penetrating the sidewalk.

Question 3

What does the “support force” exerted on the piano by the sidewalk do?

Answer 3

• acts perpendicular to the sidewalk
• is exerted upward by the horizontal surface of the sidewalk
• can cancel the piano’s downward weight
• prevents piano from falling through sidewalk

Question 4

Why does the sidewalk support the piano perfectly?

Answer 4

The sidewalk and piano negotiate by denting and indenting.