Physics; Chapter 8

centripetal force

A force that causes an object to move in a circle

Consider someone in a rotating space habitat. Rotational motion provides __. A) a support force B) gravity C) an inertial force

A) a support force

when a rotational speed of a rotating system doubles, its angular momentum __. A) doubles B) quadruples C) reduces to zero D) remains unchanged

A) doubles

what is required to change the angular momentum of a system? A) external torque B) torque C) external force D) force

A) external torque

the torque ecerted by a crowbar on an object increases with increased __. A) force and leverage distance B) force C) energy of application D) rotational inertia

A) force and leverage distance

how does a lever arm change if you decrease the angle of force? A) it decreases B) it stays the same C) it increases

A) it decreases

rotational version of Newton's first law

An object or system of objects will maintain its angular momentum unless acted upon by an external net torque.

the tangential speed on the outer edge of a rotating carousel is __. A) the same as the forward speed B) less than towards the center C) greater than toward the center D) four times as great as twice the distance

C) greater than toward the center

rotational inertia about the midpoint of an object becomes greater with __. A) increased mass B) decreased mass and decreased distance to mass concentration C) increased mass and increased distance to mass concentration D) decreased mass

C) increased mass and increased distance to mass concentration

how does the force needed to turn the wrench change when you decreases the distance to the nut? A) it stays the same B) it increases C) it decreases

C) it decreases

Consider someone in a rotating space habitat. The outward force felt by the person __. A) is real in a traditional sense B) is an interaction with earth C) is a form of gravity D) has no reaction counterpart

D) has no reaction counterpart

centrifugal force

an apparent force that acts outward on a body moving around a center, arising from the body's inertia.

distinguish between linear momentum and angular momentum

angular momentum depends on the distribution of mass. linear momentum depends on the total mass.

the center of gravity of a basketball is located __. A) at the point of application when balanced B) at its geocentrical center C) at a point opposite of its center of mass D) in the material making up its mass

b0 at its geocentrical center

tangential speed =

linear speed

linear speed =

momentum

tangential speed formula

radial distance x rotational speed (v = r x w)

external net torque

required to change the angular momentum of an object

torque

the tendency of a force to cause rotation

in order to maintain circular motion, __.

we need a change in velocity/ direction

circular motion

when an object turns about an internal axis, it is undergoing circular motion or rotation

a lever arm depends upon:

where force is applied and the direction in which it acts

when a rock tied to a string whirled in a horizontal circle somehow doubles in mass but keeps the same speed, the string tension __. A) decreases B) doubles C) increases by four D) remains the same

B) doubles

how does the force needed to turn the wrench change if you increase the lever arm? A) it stays the same B) it decreases C) it increases

B) it decreases

torque depends on three factors:

magnitude of force, the magnitude in direction in which it acts the point at which it is applied on the object

formula for centripetal force

mass x tangential speed^2 / radius

angular momentum formula

moment of inertia x angular velocity (L = I x w)

rotational speed

the number of rotations of revolution per unit time (symbol w)

rotational inertia

the property of an object to resist changes in its rotational state of motion

if you are wearing a seatbelt in a car that rounds a curve, and you slide across your seat and slam against a car door, what kind of force is responsible for your slide: A) centripetal B) centrifugal C) no force

C) no force; (there is no force as viewed by someone outside the car. to them you are moving in a straight line)

angular momentum is

the "inertia of rotation" of rotating objects

tangential

the distance traveled by a point on the rotating object divided by the time taken to travel that distance

when a rock tied to a string is whirled in a horizontal circle, doubling the speed __. A) doubles the velocity, but the string tension remains the same B) decreases the velocity C) quadruples the tension in the string D) doubles the tension in the string

C) quadruples the tension in the string