In previous lessons we learned about different types of energy, the law of conservation of energy and work.

Now that we've learned about rotational motion, there's one more type of energy we need to learn about: rotational kinetic energy. This is the energy of an object or system due to its rotational motion, instead of its translational or linear motion. The equation for rotational kinetic energy is very similar to the equation for translational kinetic energy, we just use the rotational inertia instead of mass and angular speed instead of linear speed.

Now when we use the law of conservation of energy we can include rotational kinetic energy as well. Rotational kinetic energy is not conserved on its own (unlike angular momentum), it's just another type of energy like translational kinetic energy or gravitational potential energy.

But what causes an object or system's rotational kinetic energy to change? We learned that a net torque causes an object to rotate with an angular acceleration, so a net torque will do work on an object or system to change its rotational kinetic energy (just like a net linear force can do work to change a systems translational kinetic energy).

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Free-Response Questions

Energy

• 2024 Q1 - - Block sliding on a track with loops, forces, FBDs, circular motion, energy
• 2024 Q2 - - (Experimental design) Masses oscillating on a spring, simple harmonic motion, energy, momentum
• 2024 Q5 - - Collision of two blocks, momentum, energy, forces
• 2023 Q1 - - Cart oscillating on horizontal spring, simple harmonic motion, energy, work
• 2023 Q4 - - Block hanging from string around pulley, rotational motion, torque, angular momentum, energy, work
• 2023 Q5 - - Sphere and rod rotating about axle, rotational motion, torque, energy, work
• 2022 Q1 - - Pulley system with 2 blocks and a spring, kinematics, forces, energy, work
• 2022 Q3 - - (Experimental design) Block hanging from string around wheel, energy, rotational motion
• 2022 Q5 - - Mass oscillating on a vertical spring, simple harmonic motion, energy, work
• 2021 Q1 - - Cyclist on ramp jumps over cars, kinematics, projectile motion, energy, work
• 2021 Q4 - - Cylinder rolls and block slides down an incline, energy, work, rotational motion
• 2019 Q1 - - Plunger pushes block and sphere across surface, kinematics, forces, energy, work, torque, angular momentum
• 2019 Q3 - - (Experimental design) Sphere is launched with a spring plunger, projectile motion, energy
• 2018 Q5 - - Block dropped on another oscillating block, energy, momentum, simple harmonic motion
• 2017 Q4 - - Blocks launched from slides on tables, projectile motion, energy
• 2016 Q1 - - Wheel rolls down an incline, forces, FBDs, energy, friction
• 2016 Q2 - - (Experimental design) Testing collisions for a ball, energy
• 2016 Q3 - - Cart rolls down an incline with bumps, kinematics, energy
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• Khan Academy - Rotational kinetic energy

• Organic Chemistry Tutor - Rotational Kinetic Energy
• Michel van Biezen - Hollow Ball Rolling Down an Incline

In previous lessons we learned about different types of energy, the law of conservation of energy and work.

Now that we've learned about rotational motion, there's one more type of energy we need to learn about: rotational kinetic energy. This is the energy of an object or system due to its rotational motion, instead of its translational or linear motion. The equation for rotational kinetic energy is very similar to the equation for translational kinetic energy, we just use the rotational inertia instead of mass and angular speed instead of linear speed.

Now when we use the law of conservation of energy we can include rotational kinetic energy as well. Rotational kinetic energy is not conserved on its own (unlike angular momentum), it's just another type of energy like translational kinetic energy or gravitational potential energy.

But what causes an object or system's rotational kinetic energy to change? We learned that a net torque causes an object to rotate with an angular acceleration, so a net torque will do work on an object or system to change its rotational kinetic energy (just like a net linear force can do work to change a systems translational kinetic energy).

Multiple-Choice Questions