Conservation Of Energy 1

1. The _____ states that the energy in a closed, isolated system can neither be created nor destroyed.

Law of conservation of energy

Law of conservation of mass

Law of mechanical energy

Law of thermal energy

The law of conservation of energy states that the energy in a closed, isolated system can neither be created nor destroyed. This means that the total amount of energy in the system remains constant over time. Energy can only be transferred or transformed from one form to another. This principle is a fundamental concept in physics and is applicable to various systems and phenomena.

Explanation

The law of conservation of energy states that the energy in a closed, isolated system can neither be created nor destroyed. This means that the total amount of energy in the system remains constant over time. Energy can only be transferred or transformed from one form to another. This principle is a fundamental concept in physics and is applicable to various systems and phenomena.

2.

The point at which the block has both kinetic and potential energy is .

A

B

C

Option B is the correct answer because at the highest point of its trajectory, the block has maximum potential energy due to its height above the ground. At the same time, it also has zero kinetic energy because it momentarily comes to a stop before changing direction and falling back down. This combination of potential and kinetic energy is unique to this point in the block's motion.

Explanation

Option B is the correct answer because at the highest point of its trajectory, the block has maximum potential energy due to its height above the ground. At the same time, it also has zero kinetic energy because it momentarily comes to a stop before changing direction and falling back down. This combination of potential and kinetic energy is unique to this point in the block's motion.

3.

The block has the maximum amount of kinetic energy at point

A

B

C

At point A the object has potential energy (GPE) and no kinetic energy.
At point C all the potential energy is converted to kinetic energy. (no energy lost)

Explanation

At point A the object has potential energy (GPE) and no kinetic energy.
At point C all the potential energy is converted to kinetic energy. (no energy lost)

4. The illustration below shows a ball on a curved track. The ball starts with zero velocity at the top of the track. It then rolls from the top of the track to the horizontal part at the ground

Ignoring friction, its velocity just at the moment it reaches the ground is 14 m/s. What is the height, h, from the ground

to the top of the track?

7m

10m

14m

20m

Since no energy was lost, total energy before = total energy after KE + GPE = KE + GPE at the top of the slide KE = 0 At the bottom of the slide, GPE=0

Explanation

Since no energy was lost, total energy before = total energy after KE + GPE = KE + GPE at the top of the slide KE = 0 At the bottom of the slide, GPE=0

5. . the equation that shows the conservation of mechanical energy is ________

KE before + PE before = KE after + PE after

E = KE + PE

KE before + KE after = PE before + PE after

The equation that shows the conservation of mechanical energy is KE before + PE before = KE after + PE after. This equation states that the sum of the kinetic energy (KE) and potential energy (PE) before an event or process is equal to the sum of the kinetic energy and potential energy after the event or process. This equation is derived from the principle of conservation of energy, which states that energy cannot be created or destroyed, only transferred or transformed. Therefore, the total mechanical energy remains constant before and after the event or process.

Explanation

The equation that shows the conservation of mechanical energy is KE before + PE before = KE after + PE after. This equation states that the sum of the kinetic energy (KE) and potential energy (PE) before an event or process is equal to the sum of the kinetic energy and potential energy after the event or process. This equation is derived from the principle of conservation of energy, which states that energy cannot be created or destroyed, only transferred or transformed. Therefore, the total mechanical energy remains constant before and after the event or process.

6. . A pendulum that consist of a 2kg mass swings to a maximum vertical displacement of 17cm above its rest position. At its lowest point, the kinetic energy of the mass is equal to...

0.33 J

3.33 J

33.3 J

333 J

3333 J

Explanation

7.

A pendulum is dropped from a height of 4m as shown above. The speed of the pendulum at the lowest point of the swing is most nearly...

6m/s

7m/s

8m/s

9m/s

10m/s

When a pendulum is dropped from a height, it converts its potential energy into kinetic energy as it swings. According to the principle of conservation of energy, the total mechanical energy remains constant throughout the swing. At the lowest point of the swing, all the potential energy is converted into kinetic energy. Therefore, the speed of the pendulum at the lowest point is equal to the square root of twice the acceleration due to gravity (g) multiplied by the height (h) from which it was dropped. In this case, the speed is most nearly 9m/s.

Explanation

When a pendulum is dropped from a height, it converts its potential energy into kinetic energy as it swings. According to the principle of conservation of energy, the total mechanical energy remains constant throughout the swing. At the lowest point of the swing, all the potential energy is converted into kinetic energy. Therefore, the speed of the pendulum at the lowest point is equal to the square root of twice the acceleration due to gravity (g) multiplied by the height (h) from which it was dropped. In this case, the speed is most nearly 9m/s.

8. A 0.5kg ball is dropped from a third storey window that is 10m above the sidewalk. What is the speed of the ball just before it strikes the sidewalk?

5m/s

10m/s

14m/s

28m/s

200m/s

Explanation

9. A ball falls from a height, h, from a tower. Which of the following statements is true? .

The potential energy of the ball is conserved as it falls

The kinetic energy of the ball is conserved as it falls

The differences between the potential energy and the kinetic energy is a constant as the ball falls

The sum of the kinetic and potential energies of the ball is constant

As the ball falls, its potential energy decreases because it is moving closer to the ground. At the same time, its kinetic energy increases because it is gaining speed. However, the total mechanical energy of the ball, which is the sum of its potential and kinetic energies, remains constant. This is due to the law of conservation of energy, which states that energy cannot be created or destroyed, only transferred or transformed. Therefore, the correct statement is that the sum of the kinetic and potential energies of the ball is constant.

Explanation

As the ball falls, its potential energy decreases because it is moving closer to the ground. At the same time, its kinetic energy increases because it is gaining speed. However, the total mechanical energy of the ball, which is the sum of its potential and kinetic energies, remains constant. This is due to the law of conservation of energy, which states that energy cannot be created or destroyed, only transferred or transformed. Therefore, the correct statement is that the sum of the kinetic and potential energies of the ball is constant.

10. A 5-kg object is dropped from a height of 15m. What will the approximate velocity of the object be when it is 10m above the ground?

0 m/s

10 m/s

20 m/s

50 m/s

100 m/s

Explanation