“I’m not so smart, it’s just that I stay with problems longer.”

Clarification on Right-Hand Rule

• Your fingers (excluding the thumb) will curl along the direction of the smaller angle.

Example

A small 50-g block slides down a frictionlesssurface through height h = 20 cm and then sticksto a uniform rod of mass 100 g and length 40cm. The rod pivots about point O through angleθ before momentarily stopping. Find θ.

ExampleShown is a top view of a thin uniform rod of length0.600 m and mass M rotating horizontally at 80.0rad/s counterclockwise about an axis through itscenter. A particle of mass M/3.00 and travellinghorizontally at speed 40.0 m/s hits the rod andsticks to it. The particle’s path is perpendicular tothe rod at the instant of the hit, at a distance d fromthe rod’s center. At what value of d are the rod andparticle stationary after the hit?

Example

Refer to the conical pendulum figure. Show thatthe magnitude of the angular momentum ofthe bob about the center of the circle (thepath that the bob traces) is given by

Example

A meter stick will balance on your finger if yousupport it at its center of gravity—themidpoint. The two halves have equal weights.A broom will also balance on your finger if yousupport it at its center of gravity. Suppose youcut the broom into two parts through thecenter of gravity and weighed each part on ascale. Would their weights be equal?

Example

Tightrope walkers along high wires carry a heavyhorizontal bar. You would think that this extraweight makes each step harder to achievethan with a lighter bar. Why is this done?

Example

What happens to a discman when turned on inouter space?

Example

You have a spool of thread, already partiallyunwound as shown. You pull (slowly) on thethread. Does the spool go right or left?

Winding and Unwinding of the Spool

Problem

A body of radius R and mass m is rollingwithout slipping with speed v on a horizontalsurface. It then rolls up a hill to a maximumheight

Is the body a solid sphere, hollow sphere, solidcylinder or hollow cylinder? Support youranswer by solving the moment of inertiaabout the axis of rotation.