Concept Physics Chapter 8 Test

Work is force times

distance

Power equals work

divided by time (work done divided by time interval)

What is the ability to cause change

energy

An object at rest may have

energy.

Power and work are always equal.

false

When you do less work in a given time period, the power increases.

false

One watt is equivalent to one joule per meter.

false; joule per second

The rate in which work is done is called energy.

false; rate at which work is done - power

When a car's speed triples, its kinetic energy

increases nine times

Energy in the form of motion is

kinetic energy

Energy may change from one form to another, but it cannot be created or destroyed under ordinary conditions

law of conservation of energy

The total amount of kinetic and potential energy in a system

mechanical energy

An object that has kinetic energy must be

moving

In energy transformation

no energy is lost.

Kinetic energy of an object is equal to

one half the product of its mass times its speed squared

Potential energy the energy of an object because of its

position

Stored energy is

potential energy

A job is done slowly, and an identical job is done quickly. Both jobs require the same amount of work but different amounts of

power

What is the rate at which work is done

power

Raising an auto in a service station requires work. Raising it three times as high requires

three times the work

A rock at the edge of a cliff has potential energy because of is position.

true

Energy transforms from one form to another with no net gain or loss.

true

Gravitational potential energy depends on

weight and height (weight x height = gravitational potential energy)

Transfer of energy through motion is called

work

Centrifugal Force

An outward force apparent in a rotating frame of reference. It is apparent (fictitious) in the sense that it is not part of an interaction but is a result of rotation - with no reaction force counterpart.

The amount of work done by two boys who each apply 200 N of force in an unsuccessful attempt to move a stalled car is

0

Energy of motion is

Kinetic Energy

A unit used to measure work is

Newton-meter

One Joule of work done is the same as one

Newton-meter

Energy that is stored is called

Potential Energy

Center of Mass (CM)

The average position of the mass of an object. The CM moves as if all the external forces acted at this point.

Center of Gravity (CG)

The average position of weight or the single point associated with an object where the force of gravity can be considered to act.

Tangential Speed

The linear speed tangent to a curved path, such as in circular motion.

Rotational Speed

The number of rotations or revolutions per unit of time; often measured in rotations or revolutions per second or per minute. (Scientist usually measure it in radians per second)

Angular Momentum

The product of a body's rotational inertia and rotational velocity about a particular axis. For an object that is small compared with the radial distance, angular momentum can be expressed as the product of mass, speed, and radial distance of rotation.

Torque

The product of force and lever-arm distance, which tends to produce or change rotation: Torque = lever arm x force

Linear Momentum

The product of the mass of an object and its linear velocity

Rotational Inertia

The property of an object to resist any change in its state of rotation: If at rest, the body tends to remain at rest; if rotating, it tends to remain rotating and will continue to do so unless acted upon by an external net torque.

Equilibrium

The state of an object in which it is not acted upon by a net force or a net torque.

An empty truck traveling at 40 km/h has KE. How much KE does it have when it is loaded so its mass is twice but keeps the same speed?

Twice the Kinetic Energy

A unit of power is a

Watt

Conservation of Angular Momentum

When no external torque acts on an object or a system of objects, no change of angular momentum can occur. Hence, the angular momentum before an event involving only internal torques is equal to the angular momentum after the event.

A 6 kg object moves at 2 m/s. Its kinetic energy is

12 joules

What is the work done in lifting 60 kg of blocks to a height of 20 m?

1200 joules

The amount of work done when a force of 300 N moves an object a distance of 2 m is

600 J

One horsepower is about the same as

750 Watt

Centripetal Force

A force directed toward a fixed point, usually the cause of circular motion: F=mv²/r