Concepts of Physics

Exactly what is it that enables an object to do work? Heat Energy Impulse Momentum

Energy

When the speed of a moving car is doubled, how much more kinetic energy does it have? It has half as much. It has four times as much. It has the same kinetic energy. It has twice as much.

It has four times as much.

Compared with a car moving at some original speed, how much work must the brakes of a car supply to stop a car that is moving twice as fast? How will the stopping distances compare? There is no change in the work and stopping distance. It takes four times the work and four times the stopping distance. It takes twice the work and twice the stopping distance. It takes half the work and half the stopping distance.

It takes four times the work and four times the stopping distance.

Part A Two identical cars are driving in opposite directions at the same speed. Their kinetic energies have ____. different magnitudes and opposite signs the same magnitude and sign different magnitudes, but the same sign the same magnitude, but opposite signs Part B A motorcycle drives up a steeply inclined ramp. The work done on the motorcycle by the Earth's gravitational force is ____. zero negative positive Part C During a certain time interval, the net work done on an object is zero joules. We can be certain that ____. the object was at rest during this entire interval the object was at rest at the end of this interval the object's final speed was the same as its initial speed

Part A the same magnitude and sign Part B negative Part C the object's final speed was the same as its initial speed

If you push a crate horizontally with 100 N across a 10-m factory floor and the friction between the crate and the floor is a steady 70 N, how much kinetic energy does the crate gain? 700 J 400 J 1,000 J 300 J

100-70=30 30*10=300 300 J

How much work is done on a satellite in a circular orbit about Earth? The weight of the satellite times the circumference of the orbit The gravity force on the satellite times the diameter of the orbit Zero The mass of the satellite times the circumference of the orbit

Zero

When traveling twice as fast your kinetic energy is increased _______. by a factor of two. not at all. by a factor of four. by a factor of three.

by a factor of four.

Energy cannot be _______. transferred, transformed, or destroyed. transferred. transformed. destroyed.

destroyed.

What is the unit of work? joule kg m/s newton watt

joule

Consider a bob attached by a string, a simple pendulum, that swings to and fro. (Figure 1) Part A Why doesn't the tension force in the string do work on the pendulum? Drag the terms on the left to the appropriate blanks on the right to complete the sentences. parallel perpendicular Part B Explain, however, why the force due to gravity on the pendulum at nearly every point does do work on the pendulum. Drag the terms on the left to the appropriate blanks on the right to complete the sentences. mass period parallel kinetic energy perpendicular total amount of energy Part C What is the single position of the pendulum where "no work by gravity" occurs? at the pendulum's highest points between the highest and lowest points at the pendulum's lowest point This point does not exist.

Part A Tension in the string is everywhere perpendicular to the arc of the pendulum, with no component of tension force parallel to its motion. Part B In the case of gravity, a component of gravitational force on the pendulum exists parallel to the arc, which does work and changes the kinetic energy of the pendulum. Part C at the pendulum's lowest point