Annoucements #

HW 13 due tonight
HW 14 due fri
Quiz 7 posted due 4/16
Centripetal force lab due Fri
Recitation today: attend either session
Lab on Thurs: attend either session
Schedule update by thurs

Today #

More centripetal force

Clicker questions #

Problems #

Ball hanging from pendulum inside moving car turning at 10 mph, what is the radius of the turn?

How fast can a car travel and make a turn without slipping? (Assume road is perfectly flat). What is the force thats bending the car in a circle? The friction of the tires.

The maximum is when $f_s$ reaches $\mu _sn$

A car is safely negotiating an unbanked circular turn at a speed of 21 m/s. The maximum static frictional force acts on the tires. Suddently a wet patch in the road reduces the maximum static frictional force by a factor of three. If the car is to continue safely around the curve, to what speed must the drive slow the car?

A banked turn

Formulas for friction/banked turning

Acceleration in the y direction is just gravity

Orbits #

The force that pulls the apple toward the earth is the same force that keeps the moon in orbit. The force of gravity isn’t a constant, it depends on the distance away from the object squared.

The force is directly proportional to the mass involved. Inversely proportional to the distance separation squared.

Gravitational force is always an attractive force.

$r$ is the distance from the center of the earth, so as you get farther away the gravitational force becomes smaller.