3.2 Non-uniform motion

3 of 3 objectives have lessons · 0 studied · 0 secure

Lessons

Friction and drag: the forces that fight backFriction acts where surfaces touch and drag acts on anything moving through a fluid; both oppose motion, and drag grows as speed increases. 5 min, not started
Falling with air resistance: the skydiver's storyA falling object speeds up, so the air resistance grows, so its acceleration shrinks from g towards zero until drag balances weight at terminal velocity. 5 min, not started
Terminal velocity: parachutes, raindrops and top speedsAnything moving against a resistive force that grows with speed reaches a terminal velocity when that force balances the driving force; a parachute gives a new, lower one. 5 min, not started
Thrown up, thrown across: air resistance changes the tripWith air resistance, a ball thrown upwards decelerates by more than g going up and accelerates by less than g coming down; a projectile's path is lower, shorter and lopsided. 5 min, not started

Syllabus objectives

3 objectives

What Cambridge says you should be able to do, in our words. Codes are the topic number plus the objective’s position.

3.2.1

Show a qualitative understanding of friction and of viscous (drag) forces, air resistance among them.

No treatment of the coefficients of friction and of viscosity is required; a simple model in which drag force increases as speed increases is sufficient.

Taught in: Friction and drag: the forces that fight back · 6 questions

3.2.2

Describe and explain, qualitatively, the motion of an object in a uniform gravitational field when air resistance acts on it.

Taught in: Falling with air resistance: the skydiver's story, Terminal velocity: parachutes, raindrops and top speeds, Thrown up, thrown across: air resistance changes the trip · 14 questions

3.2.3

Understand that, when an object moves against a resistive force, it may reach a terminal (constant) velocity.

Taught in: Falling with air resistance: the skydiver's story, Terminal velocity: parachutes, raindrops and top speeds · 9 questions