All High School Physics Resources
Example Questions
Example Question #11 : Circular Motion
A ball attached to a string is moving counterclockwise in a vertical circle. If the string is cut exactly at the point where the ball is at the top of its motion (the top of the circle), what direction will the ball move in initially?
Downward
Upward
Right
Left
Left
In circular motion, velocity is tangential to the circular path. Since the object is moving counterclockwise, at the top of the circle this tangent line points to the left. It may help to draw a diagram to better visualize this motion.
Example Question #13 : Circular Motion
Conceptual
Two children sit on a merry-go-round. One sits from the center, and the other sits from the center. If the children are in a straight line form the center, which child has a greater speed?
The child from the center
We must know the acceleration to draw a conclusion
We must know the period to draw a conclusion
The child from the center
They have the same speed
The child from the center
Velocity is given by distance per unit time.
When moving in a circle, the distance is the circumference, and each rotation takes exactly one period. We can substitute into the velocity formula.
If the children are in a straight line, that means that their periods (how long it takes to make one revolution) will be the same. The only thing that changes is r, the distance from the center. Since radius is in the numerator, we can conclude that increasing the distance from the center will increase the velocity.
Example Question #221 : High School Physics
Two children sit on a merry-go-round. One sits from the center, and the other sits from the center. If the children are in a straight line from the center, which child has a greater speed?
We must know the acceleration to draw a conclusion
The child from the center
They have the same speed
The child from the center
We must know the period to draw a conclusion
The child from the center
Velocity is given by distance per unit time.
When moving in a circle, the distance is the circumference, and each rotation takes exactly one period. We can substitute into the velocity formula.
If the children are in a straight line, that means that their periods (how long it takes to make one revolution) will be the same. The only thing that changes is , the distance from the center. Since radius is in the numerator, we can conclude that increasing the distance from the center will increase the velocity.
Example Question #13 : Understanding Circular Motion
A rider on a Ferris wheel moves in a vertical circle of radius r at constant speed v. Is the normal force that the seat exerts on the rider at the top of the wheel?
Less than the force the seat exerts at the bottom of the wheel
More than the force the seat exerts at the bottom of the wheel
The same as the force the seat exerts at the bottom of the wheel
Less than the force the seat exerts at the bottom of the wheel
The centripetal force is what is acting on the rider. At the top of the Ferris wheel, the normal force is pointing up, and the gravitational force is pointing down. The sum of these two forces must equal the centripetal force pointing downward toward the center of the circle. Therefore the normal force must be smaller than the gravitational force. At the bottom of the Ferris wheel, the same forces are present. However, the sum of these forces must equal the centripetal force point upward toward the center of the circle. Therefore the normal force must be greater than the gravitational force. Since the normal force must be greater than the gravitational force at the bottom and less than the gravitational force at the top, the force at the bottom must be greater than the force on the top.
Example Question #1 : Using Circular Motion Equations
A ball rolls around the edge of a circle with a radius of . If it is rolling at a speed of , what is the centripetal acceleration?
Centripetal acceleration is the acceleration towards the center when an object is moving in a circle. Though the speed may be constant, the change in direction results in a non-zero acceleration.
The formula for this is , where is the perceived tangential velocity and is the radius of the circle.
Plug in the given values and solve for the acceleration.
Example Question #1 : Using Circular Motion Equations
A ball rolls around the edge of a circle with a radius of . If it is rolling at a speed of , what is the centripetal force?
Centripetal force is the force that constantly moves the object towards the center; it is what keeps the object moving in a circle rather than flying off tangentially to the circle.
The formula for force is .
To find the centripetal force, we need to find the centripetal acceleration. We do this with the formula , where is the perceived tangential velocity and is the radius of the circle.
Plug in the given values and solve for the acceleration.
Plug that into the first equation to solve for the force.
Example Question #222 : High School Physics
A ball rolls around the edge of a circle with a radius of . If it is rolling at a speed of , what is the period of the ball?
The period, , of an object moving in circular motion is the amount of time it takes for the object to make one complete loop of the circle.
If we start with the linear understanding of velocity,, we can apply the same concept here. Our velocity should be the change in distance over the change in time. In this case, we don't have a definite time, , but we do have a period in terms of one complete loop.
We can set up an equation for the period using the circumference of the circle as our distance: .
Plug in the given values to solve for the period.
Example Question #14 : Circular Motion
A ball rolls around the edge of a circle with a radius of . If it is rolling at a speed of , what is the centripetal acceleration?
Centripetal acceleration is the acceleration towards the center when an object is moving in a circle. Though the speed may be constant, the change in direction results in a non-zero acceleration.
The formula for this is , where is the perceived tangential velocity and is the radius of the circle.
Plug in the given values and solve for the acceleration.
Example Question #16 : Circular Motion
A ball rolls around the edge of a circle with a radius of . If it is rolling at a speed of , what is the centripetal force?
Centripetal force is the force that constantly moves the object towards the center; it is what keeps the object moving in a circle rather than flying off tangentially to the circle.
The formula for force is .
To find the centripetal force, we need to find the centripetal acceleration. We do this with the formula , where is the perceived tangential velocity and is the radius of the circle.
Plug in the given values and solve for the acceleration.
Plug the acceleration and given mass into the first equation to solve for force.
Example Question #3 : Using Circular Motion Equations
A ball rolls around the edge of a circle with a radius of . If it is rolling at a speed of , what is the period of the ball?
The period, , of an object moving in circular motion is the amount of time it takes for the object to make one complete loop of the circle.
If we start with the linear understanding of velocity,, we can apply the same concept here. Our velocity should be the change in distance over the change in time. In this case, we don't have a definite time, , but we do have a period in terms of one complete loop.
We can set up an equation for the period using the circumference of the circle as our distance: .
Plug in the given values to solve for the period.