{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Rotation and Torque

# Rotation and Torque - PHY121 Physics for the Life Sciences...

This preview shows pages 1–6. Sign up to view the full content.

Lecture 7 1 PHY121 – Physics for the Life Sciences I Lecture 7 1. Rotational Dynamics : Torque 2. Newton’s Law for Rotations 3. Rotational Inertia: Moment of Inertia Note: set your Clicker to Channel 21 2/14/2012

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Lecture 7 2 Recap: Newton’s Gravity Gravitational attraction is the force acting between objects that have a “ gravitational charge ”, i.e. gravitational mass (one of the mysterious facts of nature is that inertial mass and gravitation charge are proportional (or identical – in SI units) to another! This, among other facts, led Einstein to the Theory of Relativity) Force of Gravity between point-masses m 1 and m 2 at distance r 12 from one another: Magnitude : Gm 1 m 2 / r 12 2 , INIFINTE RANGE with G = 6.673×10 –11 Nm 2 /kg 2 Direction: attractive; notation: r 1 2 is pointing outwards • For SPHERICALLY SYMMETRIC objects: as if all mass was at center! e.g. on mass m by M E of Earth at sealevel : 1 ,1 on 2 1 1 2 2 2 2 G m m r G F r 2 E G E R mM G F j extremely weak for “normal” masses 2 E E GM g R 11 24 2 6 6.67 10 5.97 10 6.38 10 2 9.80m/s m g   j 2/14/2012