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For the following systems, draw free-body diagrams and explain what real force(…

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Wize University Physics Textbook (Master) > Circular Motion

Centripetal Acceleration and Centripetal Force

4 Activities

checklist
Mark Yourself Question
  1. Grab a piece of paper and try this problem yourself.
  2. When you're done, check the "I have answered this question" box below.
  3. View the solution and report whether you got it right or wrong.
For the following systems, draw free-body diagrams and explain what real force(s) is/are providing the centripetal force.
  1. The moon orbiting around the earth
  2. Being in the Gravitron amusement ride (inside, the people are stuck against the walls while the ride spins extremely fast - see picture below)
  3. Throwing the ball around the post in tetherball
  4. A car turning around a circular track
Image source: Wikimedia commons
More Centripetal Acceleration and Centripetal Force Questions:
Two strings on a spinning rod - solving
Practice: Two Strings on Spinning Rod
The 4.00-kg block in the figure is attached to a vertical rod by means of two strings. When the system rotates about the axis of the rod, the strings are extended as shown in the diagram and the tension in the upper string is 80.0 N.
Vertical circular motion
Practice: Vertical String
A box of mass 2.50 kg is attached to a string and whirled in a vertical circle of radius 1.0 m. At the exact top of the path, the tension in the string is 3 times the ball’s weight.
Ball on a string at an angle
Practice: Ball on String at an Angle
A 2.0 kg ball is suspended by a 1.20 m long string. A girl grabs the string and swings it downwards in front of her at a constant speed. The string makes an angle of 35º with the vertical. Determine the speed of the ball.
Because of Earth's rotation about its axis, a point at the poles has no centripetal acceleration. (Assume Earth is a uniform sphere and take g=9.800 ms2. g=9.800\ \frac{m}{s^2}.\ )
A wheel of radius 14.0 m is turning about a horizontal axis through its center. The linear speed of a passenger on the rim is constant and equal to 7.00 m/s.
(a) What are the magnitude and direction of the passenger's acceleration as she passes through the lowest point in her circular motion?
(b) Repeat part (a), but for the highest point instead of the lowest.
Ball on a string at an angle
A 2.0 kg ball is suspended by a 1.20 m long string. A girl grabs the string and swings it downwards in front of her at a constant speed. The string makes an angle of 35º with the vertical. Determine the speed of the ball.
A puck of mass m slides on a frictionless table while attached to a hanging cylinder of mass M by a cord through a hole in a table. What is the angular momentum of the puck?
(Hint: find the speed of the puck by considering uniform circular motion - what is the force providing the centripetal acceleration?)
Practice: Sliding off of a globe
A child is sliding on a spherical pile of snow of radius R. The child is initially at rest at the very top of the hemisphere, but is given a slight push to start sliding down. Neglect friction.
Energy conservation and circular motion
A compressed spring is used to propel a 25-gram ball-bearing along a frictionless horizontal track which contains a circular vertical loop of radius 0.30 m in a vertical plane. The spring obeys Hooke's law and is compressed 20 cm by a force of 5.0 N.
a) What is the speed of the ball-bearing at the top of the loop? Treat the ball bearing as a point mass.
b) What is the minimum spring compression required to have the ball-bearing complete a full loop?
Tension and centripetal force
The 4.00-kg block in the figure is attached to a vertical rod by means of two strings. When the system rotates about the axis of the rod, the strings are extended as shown in the diagram and the tension in the upper string is 80.0 N.
Two strings on a spinning rod - setup, approach
The 4.00-kg block in the figure is attached to a vertical rod by means of two strings. When the system rotates about the axis of the rod, the strings are extended as shown in the diagram and the tension in the upper string is 80.0 N.
Set up the problem (a free-body diagram, find unknown angles and distances, define coordinates) and then go to the next activity. Ask yourself: how do we deal with the rpm quantity in part (b)?
Vertical circular motion
A box of mass 2.50 kg is attached to a string and whirled in a vertical circle of radius 1.0 m. At the exact top of the path, the tension in the string is 3 times the ball’s weight.
A small car with mass 0.800 kg travels at constant speed on the inside of a track that is a vertical circle with radius 5.00 m (Fig.). If the normal force exerted by the track on the car when it is at the top of the track (point B) is 6.00 N, what is the normal force on the car when it is at the bottom of the track (point A)
Driving in a circle
You are driving around a sharp corner, going clockwise. There is a box in the middle of your back seat. If you are driving fast enough, the box will slide to a side of your car. Which side will it slide to? Why?
(Hint: even if questions do not ask you to draw a sketch or picture, you should draw one anyway! It makes life easier for both you and the exam marker.)
air puck problem
An air puck of mass m1=0.25 kg{\small m_1=0.25\ kg} is tied to a string and allowed to revolve in a circle of radius R = 1.0 m on a frictionless horizontal table. The other end of string passes through a hole in the center of the table, and a mass of m2=1.0 kg{\small m_2=1.0\ kg} is tied to it (Fig.). The suspended mass remains in equilibrium while the puck on the tabletop revolves.
Ball on a string at an angle
A 2.0 kg ball is suspended by a 1.20 m long string. A girl grabs the string and swings it downwards in front of her at a constant speed. The string makes an angle of 35º with the vertical. Determine the speed of the ball.
Circular Motion
A 20-g marble is free to slide on a frictionless wire loop with radius of 15 cm. The loop starts to rotate about its vertical axis until the bead slides up to θ=60∘ as shown below. What is the angular velocity of the loop at this moment?
A point object travelling in a circle must always have a net force acting on it.
Centripetal force
When an object experiences uniform circular motion, the direction of the net force is
A ball of mass 5 kg and charge Q is performing uniform circular motion on a horizontal surface. The radius of rotation is R=1m and the period of rotation is T=5 s.
If the ball is attached to a spring with equilibrium length of 0.5 m, what is the spring constant?
Assume we put another charge with the same magnitude at the origin for maintaining the circular motion. What is the type and magnitude of the charge?
The 4.00-kg block is Fig. is attached to a vertical rod by means of two strings. When the system rotates about the axis of the rod, the strings are extended as shown is the diagram and the tension in the upper string is 80.0 N. (a) What is the tension in the lower cord ? (b) How many revolutions per minute does the system make ? (c) Find the number of revolution per minute at which the lower cord just goes slack. (d) Explain what happens if the number of revolutions per min is less than in part c.
In the 'Giant swing' , the seat is connected to two cables as shown in Fig. , one of which is horizontal.The seat swings in a horizontal circle at a rate of 32.0 rpm (rev/min).If the seat weighs 255 N and an 825 N person is sitting in it, find the tension in each cable.
A boy standing in one spot swings a box on a string in a horizontal circle of radius 2m around him as fast as he can. If the force of tension in the string is 100 N and the mass of the box is 30kg, how fast is the box moving? How many revolutions per minute does it make?
A ball of mass M is released from rest at a vertical height h above the ground. The ball rolls down a frictionless inclined plane and makes it to a loop the loop of radius R.
What is the velocity of the ball as it reaches to the bottom of the incline?
What is the normal force at the bottom?
A 2.0 kg ball is suspended by a 1.20 m long string. A girl grabs the string and swings it downwards in front of her at a constant speed. The string makes an angle of 35º with the vertical. Determine the speed of the ball.
If the angle that the string makes with the vertical increases, what happens to the ball speed?
Vehicles must be able to traverse a curve of radius 60.0 m safely at speeds up to 80 km/h. If the average vehicle weighs 1000 kg, what minimum coefficient of friction is required to make this possible?
A 65 kg man is riding a Ferris wheel with radius of 15 m, that moves at 1.5 rpm. Determine the normal force that the man experiences at the top of the ferris wheel and at the bottom.
A boy standing in one spot, swings a box on a string in a horizontal circle with the radius of 2m around him as fast as he can. If the force of tension in the string is 100 N and and the mass of the box is 30kg, how fast is the box moving? How many revolutions per minute does it make?