Questions from Modern Physics

Q: People often call their electric bill a power bill, yet the

People often call their electric bill a power bill, yet the quantity on which the bill is based is expressed in kilowatt-hours. What are people really being billed for?

Q: In Fig. Q9.4, how are the radial accelerations

In Fig. Q9.4, how are the radial accelerations of points at the teeth of the two sprockets related? Explain. Fig. Q9.4:

Q: Since for a particle the kinetic energy is given by K =

Since for a particle the kinetic energy is given by K = 1 2 mv2 and the momentum by

Q: To maximize the moment of inertia of a flywheel while minimizing its

To maximize the moment of inertia of a flywheel while minimizing its weight, what shape and distribution of mass should it have? Explain.

Q: A glass dropped on the floor is more likely to break if

A glass dropped on the floor is more likely to break if the floor is concrete than if it is wood. Why?

Q: When people are cold, they often rub their hands together to

When people are cold, they often rub their hands together to warm up. How does doing this produce heat? Where does the heat come from?

Q: A machine gun is fired at a steel plate. Is the

A machine gun is fired at a steel plate. Is the average force on the plate from the bullet impact greater if the bullets bounce off or if they are squashed and stick to the plate? Explain.

Q: In physical terms, explain why friction is a non conservative force

In physical terms, explain why friction is a non conservative force. Does it store energy for future use?

Q: A net force with x-component Fx acts on an

A net force with x-component Fx acts on an object from time t1 to time t2 . The x-component of the momentum of the object is the same at t1 as it is at t2, but Fx is not zero at all times betwee...

Q: A net force of 4 N acts on an object initially at

A net force of 4 N acts on an object initially at rest for 0.25 s and gives it a final speed of 5 m/s. How could a net force of 2 N produce the same final speed?