PY 131 Chapter 8: Rotational Motion

What is the Center of Mass (CM)?

A point that moves as if all the mass of an object were located there.

Does the Center of Mass have to be inside the object?

No

What is the formula for calculating the Center of Mass of a system made up of two point masses along the x-axis?

x_CM = (m_A/M)(x_A) + (m_B/M)(x_B)

What is the formula for calculating the Center of Mass of a system of many point masses?

The weighted average of the x coordinate of each point mass.

What is the correct form of Newton's Second Law for a system made up of two or more objects?

a_CM = 1/M(F_ext)

What is the net external force?

The external force acting on a system that comes from something outside the system.

What are internal forces?

Forces exerted on each other by two objects in the system, which do not contribute to F_ext.

What happens to the Center of Mass under the net external force acting on the system?

It moves like a point particle with mass M.

What is rotational motion?

The motion of rigid objects around a single line in space called the axis of rotation.

What are polar coordinates?

A more useful way to describe the motion of objects in rotational motion, using the polar coordinates r and θ.

What is the formula for angular velocity?

ω = Δθ/Δt

What is the formula for frequency?

f = 1/T

What is the formula for angular acceleration?

α = Δω/Δt

What is the formula for linear speed?

v = r×ω

What is the formula for centripetal acceleration?

a_C = r×ω^2 = v^2/r

What is the formula for tangential acceleration?

a_tan = r×α

What is uniform circular motion?

A type of motion in which the acceleration points towards the center of the circle and the object's speed is constant

What is non-uniform circular motion?

A type of motion in which the acceleration points in a non-central direction.

What is the formula for the centripetal force?

∑ _radial components F= FC=maC= mv^2 / r =mrω^2

What is the sum in the formula for centripetal force?