Physics 1001 Notes

# Dt dt so w can vary with no net torque i11 i 2 2 2

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Unformatted text preview: d away from one through the CoM Physics 1001 Notes Chapter 10: Dynamics of Rotational motion Torque • • Torque is defined by the cross product T=r x F (vector definition) or T= rFsinØ (magnitude) o r is the point where the force F is applied o Direction of T is perpendicular to r and F o Use right hand rule to determine direction Torque and acceleration • = m1a1, tan But a1, tan = r α z 1 • So r F , tan 11 = m1r12α z • i.e. τ 1z = m1r12α z • F , tan 1 16 Physics 1001 Notes • All particles in a rigid body have the same α z : o τ 1z + τ 2 z + ... = m1r12α z + m2 r22α z + ... o ∑τ iz = (∑ mi ri 2 )α z ⇒ ∑τ z = Iα z o Where I is the moment of inertia o This is the analogue of Newtons 2nd law o Net torque is I times angular acceleration o τ net = Iα Rotation and translation • • • • If the axis of a rigid body moves ; o Consider the motion vCoM of the centre of mass o Plus the rotation w about the centre of mass 1. Apply Newtons 2nd law to all forces to...
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