Pendulums - MCAT Physical

Card 0 of 63

Question

Which factors increase the maximum velocity of a pendulum?

Answer

Both the length of the pendulum's string and the angle of displacement affect the maximum velocity of the pendulum. Increasing the length of the pendulum's string and increasing the angle of displacement both increase the distance the pendulum must travel in a single period, increasing its potential energy at its maximum height, and therefore the maximum velocity at its lowest point.

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Question

What is the period of a pendulum that has a string length of 9.8m?

Answer

The key to answering this question is to recall the following important formula for a simple pendulum: .

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Question

Which of the following changes to a pendulum will affect the angular velocity?

Answer

For a pendulum, the angular velocity is given by the equation , where is the acceleration due to gravity and is the length of the pendulum. Of the available answer choices, only changing the length of the string will effect the angular velocity. does not depend on mass or the release point of the pendulum.

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Question

For a pendulum undergoing simple harmonic motion, the ratio of the weight of the pendulum and the displacement of the pendulum from the bottommost point in its path always equals __________.

Answer

Hooke’s law, which is applicable to simple harmonic motion, states the relationship between force (F) and displacement (d).

k is equal to the spring constant. The ratio of F (force) to x (displacement) will be equal to the magnitude of k. In our set-up, the force is equal to the weight of the pendulum, so the ratio of weight to displacement is equal to the spring constant. This is true of all pendulums, and is given by the equation .

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Question

Which of the following changes would increase a pendulum's frequency?

Answer

The only two factors that affect a pendulum's frequency are the acceleration due to gravity (g) and the length of the pendulum's string (L). This can be seen in the following formula: .

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Question

The frequency of a pendulum on Earth is measured to be . What will be the approximate frequency of the same pendulum on the moon?

Approximate gravity on moon is .

Answer

The frequency of a pendulum is given by the relation .

Since gravity on the moon is one sixth of the gravity on Earth, frequency on the moon will be that on earth.

If the frequency on Earth is , then the frequency of this pendulum on the moon is .

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Question

The period of a certain pendulum is . What is the period after doubling the mass at the end of the pendulum?

Answer

The period of a pendulum is given by the formula:

is the length of the pendulum arm or string, and is the acceleration due to gravity. Gravity is constant, suggesting that the only way to manipulate the period of the pendulum is by adjusting the length of the string. Doubling the length of the pendulum arm would therefore increase the period. Since mass does not appear in the equation, it has no effect on the period of a pendulum.

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Question

A pendulum is set in motion. Which of these statements correctly characterizes the mechanical energy in the system?

Answer

Mechanical energy is the sum of potential energy and kinetic energy. Mechanical energy is conserved, unless there is intervention by a non-conservative force (such as friction).

The total energy in the system is determined by how far the pendulum is raised before release, based on the initial potential energy.

The potential energy is all converted to kinetic energy as the pendulum swings through the bottom, or mid-point of its excursion.

Once the pendulum is set in motion, the mechanical energy is constant in a frictionless system.

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Question

A pendulum has a length 2 meters with a 5kg mass at the end. It has a maximum angle of 60 degrees from vertical and is hanging from the ceiling of an elevator. When the pendulum is at its highest point, the elevator begins to accelerate at a rate of . What is the the pendulum's new maximum velocity (neglecting the vertical velocity of the elevator)?

Answer

This problem covers conservation of energy in the form of a pendulum:

If the initial state is when the pendulum is at its highest point, and the final state is when the pendulum is at its lowest state, we can rewrite:

Substituting in our expressions:

Rearranging for final velocity:

We can calculate the height using the maximum angle the pendulum makes to the vertical. At this point, the pendulum covers a vertical distance of:

Therefore, the height above the lowest point is:

Now, we just need to find out what the net downward acceleration is. Normally gravity is 10, but the elevator is accelerating upward at a rate of . Therefore the percieved gravitational acceleration is .

Plugging in all of our values:

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Question

Which factors increase the maximum velocity of a pendulum?

Answer

Both the length of the pendulum's string and the angle of displacement affect the maximum velocity of the pendulum. Increasing the length of the pendulum's string and increasing the angle of displacement both increase the distance the pendulum must travel in a single period, increasing its potential energy at its maximum height, and therefore the maximum velocity at its lowest point.

Compare your answer with the correct one above

Question

What is the period of a pendulum that has a string length of 9.8m?

Answer

The key to answering this question is to recall the following important formula for a simple pendulum: .

Compare your answer with the correct one above

Question

Which of the following changes to a pendulum will affect the angular velocity?

Answer

For a pendulum, the angular velocity is given by the equation , where is the acceleration due to gravity and is the length of the pendulum. Of the available answer choices, only changing the length of the string will effect the angular velocity. does not depend on mass or the release point of the pendulum.

Compare your answer with the correct one above

Question

For a pendulum undergoing simple harmonic motion, the ratio of the weight of the pendulum and the displacement of the pendulum from the bottommost point in its path always equals __________.

Answer

Hooke’s law, which is applicable to simple harmonic motion, states the relationship between force (F) and displacement (d).

k is equal to the spring constant. The ratio of F (force) to x (displacement) will be equal to the magnitude of k. In our set-up, the force is equal to the weight of the pendulum, so the ratio of weight to displacement is equal to the spring constant. This is true of all pendulums, and is given by the equation .

Compare your answer with the correct one above

Question

Which of the following changes would increase a pendulum's frequency?

Answer

The only two factors that affect a pendulum's frequency are the acceleration due to gravity (g) and the length of the pendulum's string (L). This can be seen in the following formula: .

Compare your answer with the correct one above

Question

The frequency of a pendulum on Earth is measured to be . What will be the approximate frequency of the same pendulum on the moon?

Approximate gravity on moon is .

Answer

The frequency of a pendulum is given by the relation .

Since gravity on the moon is one sixth of the gravity on Earth, frequency on the moon will be that on earth.

If the frequency on Earth is , then the frequency of this pendulum on the moon is .

Compare your answer with the correct one above

Question

The period of a certain pendulum is . What is the period after doubling the mass at the end of the pendulum?

Answer

The period of a pendulum is given by the formula:

is the length of the pendulum arm or string, and is the acceleration due to gravity. Gravity is constant, suggesting that the only way to manipulate the period of the pendulum is by adjusting the length of the string. Doubling the length of the pendulum arm would therefore increase the period. Since mass does not appear in the equation, it has no effect on the period of a pendulum.

Compare your answer with the correct one above

Question

A pendulum is set in motion. Which of these statements correctly characterizes the mechanical energy in the system?

Answer

Mechanical energy is the sum of potential energy and kinetic energy. Mechanical energy is conserved, unless there is intervention by a non-conservative force (such as friction).

The total energy in the system is determined by how far the pendulum is raised before release, based on the initial potential energy.

The potential energy is all converted to kinetic energy as the pendulum swings through the bottom, or mid-point of its excursion.

Once the pendulum is set in motion, the mechanical energy is constant in a frictionless system.

Compare your answer with the correct one above

Question

A pendulum has a length 2 meters with a 5kg mass at the end. It has a maximum angle of 60 degrees from vertical and is hanging from the ceiling of an elevator. When the pendulum is at its highest point, the elevator begins to accelerate at a rate of . What is the the pendulum's new maximum velocity (neglecting the vertical velocity of the elevator)?

Answer

This problem covers conservation of energy in the form of a pendulum:

If the initial state is when the pendulum is at its highest point, and the final state is when the pendulum is at its lowest state, we can rewrite:

Substituting in our expressions:

Rearranging for final velocity:

We can calculate the height using the maximum angle the pendulum makes to the vertical. At this point, the pendulum covers a vertical distance of:

Therefore, the height above the lowest point is:

Now, we just need to find out what the net downward acceleration is. Normally gravity is 10, but the elevator is accelerating upward at a rate of . Therefore the percieved gravitational acceleration is .

Plugging in all of our values:

Compare your answer with the correct one above

Question

Which factors increase the maximum velocity of a pendulum?

Answer

Both the length of the pendulum's string and the angle of displacement affect the maximum velocity of the pendulum. Increasing the length of the pendulum's string and increasing the angle of displacement both increase the distance the pendulum must travel in a single period, increasing its potential energy at its maximum height, and therefore the maximum velocity at its lowest point.

Compare your answer with the correct one above

Question

What is the period of a pendulum that has a string length of 9.8m?

Answer

The key to answering this question is to recall the following important formula for a simple pendulum: .

Compare your answer with the correct one above

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