ap physics 1 torque & rotation basics (i think)

Torque

• t_ccw  = t_cw

• f*d*sin(Θ)

• Force applied further away from the axis of rotation = more torque applied

Rotational Inertia

• I = cmr²

• Hoop = I = mr²

• Objects with a larger Rotational Inertias are harder to rotate, and harder to stop

• The further away mass is distributed from the axis of rotation, the larger the rotational inertia.

Newton’s Second Law (angular edition)

Angular acceleration = Σt (net torque) / I (rotational inertia)

Rotational Kinetic Energy

• K_rotational = ½ Iꞷ²

• K_{translational} = ½ mv²

• If an object’s center of mass is moving and the object is rotating, it has both translational (linear) and rotational kinetic energy.

Angular Momentum

• L = Iꞷ

• L = mv(rsinΘ)

• L = mv(r)

• ΔL = t (torque) Δt (time)

Gravitational Orbit Energy (U_g)

• When U_g = mgh cannot be used, use

  U_g = -G (m₁m₂/d)

• WILL ALWAYS BE NEGATIVE OR ZERO

• G = 6.67*10^-11 N m²/kg²