Podcast
Questions and Answers
A ball is swung in a horizontal circle. Which force acts as the centripetal force?
A ball is swung in a horizontal circle. Which force acts as the centripetal force?
A car is traveling around a circular track at a constant speed. What is the direction of the car's acceleration?
A car is traveling around a circular track at a constant speed. What is the direction of the car's acceleration?
A ball is attached to a string and swung in a vertical circle. At what point in the circle is the tension in the string the greatest?
A ball is attached to a string and swung in a vertical circle. At what point in the circle is the tension in the string the greatest?
A ball is moving in a horizontal circle. The ball is suddenly released. What is the path of the ball immediately after it is released?
A ball is moving in a horizontal circle. The ball is suddenly released. What is the path of the ball immediately after it is released?
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A car is traveling around a circular curve. If the car's speed is doubled, what happens to the centripetal force required to keep the car moving in a circle?
A car is traveling around a circular curve. If the car's speed is doubled, what happens to the centripetal force required to keep the car moving in a circle?
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A ball is spinning inside a cone. If the ball spins too fast, what happens to the direction of friction?
A ball is spinning inside a cone. If the ball spins too fast, what happens to the direction of friction?
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A ball is swung in a vertical circle. At what point in the circle is the tension in the string the least?
A ball is swung in a vertical circle. At what point in the circle is the tension in the string the least?
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A satellite is in a circular orbit around the Earth. What provides the centripetal force that keeps the satellite in orbit?
A satellite is in a circular orbit around the Earth. What provides the centripetal force that keeps the satellite in orbit?
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A ball is moving in a vertical circle. If the ball is moving too slowly at the top of the circle, what will happen?
A ball is moving in a vertical circle. If the ball is moving too slowly at the top of the circle, what will happen?
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What is the relationship between the angular velocity (ω) and the period (T) of a rotating object?
What is the relationship between the angular velocity (ω) and the period (T) of a rotating object?
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Study Notes
Angular Velocity
- Angular velocity is the rate of change in angle with respect to time, measured in rad/s and symbolized by ω.
Periodic Time
- Periodic time is the time it takes for one full revolution to occur, measured in seconds and symbolized by T.
Centripetal Force
- Centripetal force is responsible for keeping an object moving in a circle, constantly changing direction.
- Sources of centripetal force include: • Tension • Weight • Reaction force • Friction
- Centripetal force always points towards the center of the circle.
Horizontal Circular Motion
- To solve problems involving horizontal circular motion: • Draw a force diagram for the object • Set vertical forces up and down equal to each other • Set total horizontal force equal to centripetal force • Combine equations and solve for unknowns
Friction
- To find the direction of friction, imagine which direction the object would move if the surface was smooth, and friction acts in the opposite direction.
- Examples: • Friction acts down and in if a ball is spinning too fast inside a cone and spirals up. • Friction acts up and out if a ball is spinning too slow inside a cone and spirals down.
Vertical Circular Motion
- The speed of an object in vertical circular motion is always changing as energy is converted between kinetic and potential energy.
- Conservation of energy must be used to solve problems involving vertical circular motion.
Strings and Tension
- Centripetal force in vertical circular motion comes from a combination of tension and a component of the object's weight.
- At the bottom of the circle, F = T - W, and tension is greatest.
- At the top of the circle, F = T + W, and tension is smallest.
- Tension in the string continuously changes, and if it reaches 0, the string goes slack.
- If a particle only just reaches the top, the string goes slack at that point.
Loops
- If a particle is moving along a loop, it feels a reaction force with the surface.
- To find when/where the particle falls off the loop, find when the reaction force becomes zero.
- If a particle is moving on a loop, the reaction force R acts in the opposite direction to the centripetal force.
- If a particle is moving inside a loop, R provides the centripetal force.
- Another way to find when a particle loses contact with the inside of a loop is to see when its speed becomes 0.
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Description
This quiz covers key concepts in circular motion, including angular velocity, periodic time, centripetal force, and centripetal acceleration.
