Transcript Slide 1
Rotational Motion Uniform Circular Motion The object’s speed is constant but its direction is changing. Important to driving (how fast can I take a curve on the road?) and satellites in orbit 7/17/2015 APHY101 1 Rotational Motion Period 7/17/2015 The time to return to the original position. APHY101 2 Rotational Motion Centripetal Acceleration The acceleration of an object moving along a circular path. v ac 7/17/2015 APHY101 3 Rotational Motion Newton’s 2nd Law and Centripetal Acceleration What is the force that causes an object to accelerate in a circle? • Tension, gravity, friction, etc. 7/17/2015 APHY101 4 Rotational Motion Artificial Gravity Rotation causes the normal force which is assumed to be the force of gravity. Training for astronauts Missions to Mars and beyond 7/17/2015 APHY101 5 Rotational Motion Torque (τ ) A force that causes or opposes rotation Depends on the net force applied and the distance of the net force from the axis of rotation. τ = Fnet r 7/17/2015 ccw is + and cw is - APHY101 6 Rotational Motion Moment of Inertia ( I ) The resistance to change in angular motion τnet = I α Similar to Newton’s 2nd Law: Fnet = m a I depends on the mass of an object’s particles and their distance from the axis of rotation 7/17/2015 APHY101 7 Rotational Motion Angular Momentum ( L ) Similar to linear momentum but includes the distance from the axis of rotation L = (mv) r m r 7/17/2015 v APHY101 8 Rotational Motion Torque and Angular Momentum A net torque applied during a time interval will change an object’s angular momentum τnet Δt = ΔL Example: riding a bicycle • Stability – bicycles, footballs, gyroscopes 7/17/2015 APHY101 9 Rotational Motion Conservation of Angular Momentum If no net, external torque is applied to an object, its angular momentum is constant. • The moment of inertia and the angular velocity will increase or decrease 7/17/2015 Examples: skaters, gymnasts, divers, helicopters APHY101 10