Question 1

If the kinetic energy of an object increases, then

Accepted Answer

Kinetic energy is directly related to the speed of an object, as it is defined by the equation $KE = \frac{1}{2}mv^2$, where $m$ is the mass and $v$ is the speed of the object. Therefore, if the kinetic energy increases, the speed of the object must also increase.

Question 2

In pole-vaulting, in addition to gravitational potential energy there is potential energy in the bent pole which is analogous to potential energy stored in a _______________ under compression.

Accepted Answer

The answer of In pole-vaulting, in addition to gravitational potential...

Question 3

A ball of mass 5 kg attached to a string is swung in a horizontal circle of radius 0.5 m. If the tension in the string is 10 N, the work done by the tension in one revolution is _____________ J.

Accepted Answer

The answer of A ball of mass 5 kg attached...

Question 4

When a force acts in a direction opposite to the motion, __________ work is said to be done on the object.

Accepted Answer

The answer of When a force acts in a direction...

Question 5

A simple machine allows you to move _________ masses even though you apply _________.

Accepted Answer

According to the statement, a simple machine allows you to move larger masses even though you apply smaller force over a longer distance. This is the principle of mechanical advantage, where a simple machine leverages the input force and distance to produce a larger output force over a shorter distance. Therefore, option A is the correct choice.

Question 6

A spring wound clock makes use of ____________ energy to drive the mechanism.

Accepted Answer

The answer of A spring wound clock makes use of...

Question 7

Total mechanical energy of a system is conserved when there are only ___________________ forces doing work on the system.

Accepted Answer

The answer of Total mechanical energy of a system is...

Question 8

Other things being equal, the pole-vaulter having the greatest __________ energy prior to going into the jump should jump the highest.

Accepted Answer

The answer of Other things being equal, the pole-vaulter having...

Question 9

If an object has a larger potential energy than kinetic energy,

Accepted Answer

The relationship between potential energy and kinetic energy does not directly determine changes in speed. The transformation between these types of energy depends on the situation, such as the forces acting on the object and its environment.

Question 10

The potential energy of a spring is 0.3 J when it is compressed 0.04 m to the left of its equilibrium position. At this point it comes to its leftmost position. What is its kinetic energy at this point?

Accepted Answer

At the leftmost position, the spring stops moving, hence its velocity becomes zero and so does its kinetic energy. Therefore, the answer is zero.

Question 11

The potential energy of a spring is 0.3 J when it is compressed 0.04 m to the left of its equilibrium position. At this point it comes to its leftmost position. What is its kinetic energy when it returns to the equilibrium point?

Accepted Answer

The potential energy at the equilibrium point is zero because the spring is neither compressed nor stretched. The kinetic energy of the spring at the equilibrium point equals the initial potential energy (0.3 J) because of the conservation of mechanical energy. The spring is moving to the right as it returns to the equilibrium position from being compressed to the left.

Question 12

The conversion of the initial potential energy of a person on a sled on a smooth icy slope into kinetic energy at the bottom is an example of the principle of conservation of _________________.

Accepted Answer

The answer of The conversion of the initial potential energy...

Question 13

Two springs are hung from a ceiling and carry identical masses. The first spring has a spring constant twice as large as the second spring. The masses on each spring are pulled down from their equilibrium positions the same distance and are then released. The amplitude of the oscillation is

Accepted Answer

The amplitude of oscillation depends on the initial displacement from the equilibrium position, not on the spring constant. Since both masses are pulled down the same distance and released, the amplitude of oscillation will be the same for both springs.

Question 14

A small radio-controlled car's motor rated at 6 watts output is capable of performing _________________ Joules of work in 15 seconds.

Accepted Answer

The answer of A small radio-controlled car's motor rated at...

Question 15

The __________ of a pendulum is the amount of time the pendulum takes for one full swing.

Accepted Answer

The answer of The __________ of a pendulum is the...

Question 16

When you lift a heavy 5.0 kg crate straight up from ground level to a height of 2.0 m above ground level, then you have changed the crate's gravitational potential energy by

Accepted Answer

The gravitational potential energy gained by an object lifted to a height h is given by mgh, where m is the mass of the object, g is the acceleration due to gravity, and h is the height. Plugging in the values given, we get (5.0 kg)(9.8 m/s^2)(2.0 m) = 98 J.

Question 17

Can the gravitational force of Earth do positive or negative work on a geosynchronous communication satellite, once it is on its circular orbit?

Accepted Answer

The gravitational force of Earth is always perpendicular to the motion of a geosynchronous communication satellite in its circular orbit, therefore it cannot do any work on the satellite. The fact that the satellite has zero acceleration and constant speed only confirms that its kinetic energy is constant, but not related to the work done by gravity. Centripetal forces always do positive work, but in this case the gravitational force is not the centripetal force, as it does not change the direction of motion of the satellite.

Question 18

A mass attached to a spring is drawn back 2 cm from equilibrium and released. If a second spring were used that had a smaller spring constant than the first but the mass was the same, which of the following would be larger?

Accepted Answer

The period of oscillation of a mass-spring system is given by $T = 2\pi\sqrt{\frac{m}{k}}$, where $m$ is the mass and $k$ is the spring constant. A smaller spring constant ($k$) would result in a larger period ($T$), as they are inversely proportional in the equation.

Question 19

A horizontal force acts on a block that is initially at rest but free to move across a smooth horizontal surface. The work done by this force ___________ (increases; does not change; decreases) the kinetic energy of the block.

Accepted Answer

The answer of A horizontal force acts on a block...

Quiz 6: Energy and Oscillations