Bellringer:

What would be the net acceleration of a 15 g toy car down a 30 degree incline if

the acceleration due to friction is 1.8 m/s2? Include a free-body diagram of all

forces.

Chapter 8 – Angular motion, torque, and moment of inertia

Angular Motion What is angular motion?

How is it different from linear motion?

Vocabulary Revolution Radian Angular displacement Angular velocity Angular acceleration

Equations 1 revolution = 2π radians Angular displacement (Θ, in rad)

Θ = d/r (linear distance in m / radius) Angular velocity (ω, in rad/s)

ω = Θ/t (also equal to v/r) Angular acceleration (α, in rad/s2)

α = ω/t (also equal to a/r)

Practice p.200 (1-3) Keep answers to number 1 in terms of π

Bellringer What is the equation to convert from linear distance to

angular displacement? What is the equation to convert from linear velocity to

angular velocity? What is the equation to convert from linear

acceleration to angular acceleration? WHAT IS SIMILAR IN ALL OF THESE

EQUATIONS? Write out the equations to find angular velocity and to

find angular acceleration.WHAT DO YOU NOTICE ABOUT THESE

EQUATIONS?

Torque What is torque?

DefinitionEquationLever arm (perpendicular distance from the axis

of rotation to the point where the force is exerted)○ L = r sin Θ when the angle is not perpendicular

Practice p.203 (11-15)11. τ = 35 Nm, L = 25 cm, F = ?

12. 0.407 m13. 36.6o

14. 94 Nm15.

Net Torque To find net torque,

use the equation:τ = Fg r

Use net torque when you have a situation with a center fulcrum and 2 lever arms

Practice p.205 (16-20)16.mA = 43 kg, rA = 1.8 m, mS = 52 kg, rS

= ?

17. 2.7 Nm18. 0.056 kg19. 0.042 kg20. 789 N

Moment of Inertia Definition Equation Compare and contrast the different

moments of inertia for various objects in Table 8-2. What object would have the highest?

Lowest?What does this mean about this object?

Practice p.208 (21 and 24)Units for moment of inertia are kgm2.21. What is the change in I when r is

increased from 0.3 m to 0.6 m?

24.

Newton’s Second Law for Rotational Motion What is Newton’s Second Law?

How does it change with rotational motion?

Practice p.210 (27)