November 2

AP Physics

Momentum Test return

In:What makes objects move in a

circle?

Objective:

To begin our study of circular motion.

Success criteria:

Discover the variables of centripetal force, and be able to do centripetal force and acceleration problems.

Discovery Lab: Circular motion

Using the circular motion device, discover everything you can about circular motion.

List your discoveries:

What did we find out?

Period (T) is the time it takes to go around once.

Frequency ( f ) the number of times it goes around in one second

T=1/ f

Centripetal acceleration

• Always toward the center

ac= v2

r

Centripetal force:

“Center seeking” force

Fc= mv2

r

Tangential Speed

V=d/t

Distance = 2πr

Time=T (period)

So…….

V= 2πr

T

Problem

• A 2.1 m rope attaches a tire to an overhanging tree limb. A girl swinging on the tire has a tangential speed of 2.5 m/s. If the magnitude of the centripetal force is 88 N, what is the girl’s mass?

A bicyclist is riding at a tangential speed of 13.2 m/s around a circular track. The magnitude of the centripetal force is 377N, and the combined mass of the bicycle and rider is 86.5 kg. What is the track’s radius?

A dog sits 1.5 m from the center of a merry-go round and revolves at a tangential speed of 1.8 m/s. If the dog’s mas is 18.5 kg, what is the magnitude of the centripetal force on the dog?

A 905 kg car travels around a circular track with a circumference of 3.25 km. If the magnitude of the centripetal force is 2140 N, what is the car’s tangential speed?

Practice Problems:

Out:

What makes objects move in a circle?