Momentum, Work, Power, and Efficiency

NS3310Dr. Hoge

Cartoon Laws of Physics Law I

Any body suspended in space will remain in space until made aware of its situation.

Law IIAny body in motion will tend to remain in motion until solid matter intervenes suddenly.

Law IIIAny body passing through solid matter will leave a perforation conforming to its perimeter.

Law IVThe time required for an object to fall twenty stories is greater than or equal to the time it takes for whoever knocked it off the ledge to spiral down twenty flights to attempt to capture it unbroken.

Law VAll principles of gravity are negated by fear.

Law VIAs speed increases, objects can be in several places at once.

Law VIICertain bodies can pass through solid walls painted to resemble tunnel entrances; others cannot.

Law VIIIAny violent rearrangement of feline matter is impermanent.

Corollary: A cat will assume the shape of its container. This is also true for ducks, Martians, Roosters, and many other cartoon characters.

Law IXEverything falls faster than an anvil.

Law XFor every vengeance there is an equal and opposite re-vengeance.

Momentump = mv

Clowns on IceLife Preserver Problem

Momentum is ConservedCollisions

Elastic Inelastic

Momentum ProblemsWhy are Boxing Gloves Safer than Bare Hands?

How Can Cats Survive Long Falls?

Bed of Nails, Anyone?

What should you do if you are trapped in a falling elevator?

ImpulseImpulse = Ft

Impulse = Dp (Impulse equals change in Momentum)

Why is it easier to accelerate a soccer ball than a bowling ball?

Can you push your van from the inside?

Why is it better to push your stalled van than to hit it?

Work

W = Fd

Force is measured in Newtons (N), or Pounds (lb)

Distance is measured in meters (m), or feet (ft)

Work is measured in Joules (J, which = 1 Nm), or Foot-Pounds (ft-lbs)

HINT: Don’t forget the units! Without units, you don’t have a complete answer. And, if you don’t have the right units at the end, you did something wrong.

PowerPower = W / t

Work is measured in Joules (J), or Foot-Pounds (ft-lbs)

Time is measured in hours or seconds (hr, s)

Power in measured in J/t (Joules per second) or horsepower (550 ft-lbs/s)

Work ProblemsHow do simple machines reduce the

amount of work?

How do gears work?

How do engines have horsepower?

Simple MachinesSimple Machines

Levers

Pulleys

Inclined Planes

Wedges

Screws

Fun with PhysicsRoller Coaster Physics

The Physics of Baseball

NASCAR Physics

Physics of Martial Arts

Movie Physics

Physics of Superheroes