Kinetic Energy
What two factors determine the kinetic energy of an object?
Mass and speed.
What type of potential energy is stored in a stretched or compressed spring?
Elastic potential energy.
In the absence of friction, how does the total mechanical energy of a system change when an object falls freely?
It remains constant as potential energy is converted into kinetic energy.
Can work be done on an object if it does not move? Why or why not?
No, because work requires displacement in the direction of the force. No movement means no work.
What is a conservative force?
A force where the work done depends only on the initial and final positions, not the path taken.
If the total energy of an object is constant but its speed increases, what must be happening to its kinetic energy?
Its kinetic energy must be increasing, as total energy is conserved and potential energy is decreasing.
If you double the mass of an object but keep its height the same, how does its gravitational potential energy change?
It doubles because gravitational potential energy is directly proportional to mass.
What does it mean when we say 'energy is conserved' in a system?
It means that the total amount of energy stays the same, but it can change forms, like from potential to kinetic energy.
If two people lift the same object to the same height, but one does it faster, who does more work?
Neither. They do the same amount of work because work depends on force and displacement, not time.
Is friction a conservative or non-conservative force?
Non-conservative, because it dissipates energy as heat and depends on the path.
If a car’s speed is tripled, by how much does its kinetic energy change?
It increases by nine times.
What’s the key difference between gravitational potential energy and elastic potential energy in terms of their sources?
Gravitational potential energy comes from an object’s position in a gravitational field, while elastic potential energy is stored in materials that can stretch or compress.
How does conservation of energy explain why a car slows down when coasting up a hill?
The car’s kinetic energy is converted into gravitational potential energy as it gains height, causing it to slow down.
A force is applied perpendicular to an object’s displacement. How much work is done by the force?
No work is done because work is the product of force and displacement in the same direction.
Can a conservative force change the total mechanical energy of a system?
No, conservative forces cannot change the total mechanical energy; they only convert between kinetic and potential energy.
Two objects with the same kinetic energy are moving, but one is much heavier than the other. How does their speed compare?
The lighter object must be moving faster because kinetic energy depends on both mass and the square of speed.
Does an object’s gravitational potential energy depend on its path to its final position? Why or why not?
No, gravitational potential energy depends only on the object’s height relative to a reference point, not on the path taken.
How does the energy in a swinging pendulum change as it moves?
The pendulum's energy switches between kinetic energy when it's moving fastest and potential energy when it's at its highest points.
In what situation can an object have energy but no power?
If the object has stored energy, like potential energy, but is not transferring or converting it (no work is being done), it has energy but no power.
How does gravity act as a conservative force when you throw a ball into the air?
Gravity converts the ball’s kinetic energy into potential energy as it rises, and then back into kinetic energy as it falls.