EXSC Mechanics Exam 3

Important factors for moment of inertia

I=mk²

If a force is directed thru the center of mass an object will

move thru a straight line

if there are 3 eccentric forces and 2 centric forces acting about the elbow how many torques are acting on the elbow

3 eccentric forces

a lever with an applied forces between the axis of rotation and the resistance forces is a ___-class lever

third

a lever with the load between the axis of rotation and the resistance is a ___-class lever

second

a lever with the axis of rotation is between the applied force and resistance load is a ___-class lever

first

Torque depends on

T=Fd(moment arm)

The moment arm associated with a torque is

a distance which is perpendicular to the force

Why is it easier for a gymnast to rotate faster in the air when they are in a tucked position rather than an extended position?

The mass of the body is concentrated more closely to the axis of rotation

Moment of Inertia of an object depends on its

the tendency of a body to resist a change in motion

When a system is in a state of static equilibrium (ie no movement)

All torques must sum to zero

According to the laws that govern angular motion, of all the following are true except

A figure skater is spinning with her arms outstretched. One second into the spin, she pulls her arms into close to her body and continues spinning. With regard to the change in body position

there is less resistance to angular motion about the longitudinal axis in the second body position

In the moment of inertia of a body increases, but angular momentum is constant what happens to its angular velocity

it decreases

Angular momentum depends on

moment of inertia and angular velocity

t or f the angular acceleration of a joint will be in the opposite direction of the net external torque

false

t or f during the follow thru of a baseball pitch, as the arm slows down the shoulder velocity and shoulder angular will both be in the direction of extension

false, to slow down they would be in opposite directions

moment arm

perpendicular from line of action to axis of rotation

radius

the line from axis of rotation to edge of circle

axis of rotation

the point in which everything rotates about

torque

the product of the force and the perpendicular distance to the axis of rotation

Moment of inertia