Physics chapters 5-8 (PRUCNAL)

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momentum

the inertia of motion

impulse is equal to:

the change in momentum

the impulse of an object can change if:

the object's mass changes and if the object's velocity changes

A rifle recoils while firing a bullet. The speed of the rifle's recoil is small because the ____.

rifle has much more mass than the bullet

Two objects have the same size and shape, but one is much heavier than the other. When they are dropped simultaneously from a tower, they reach the ground at the same time, but the heavier one has a greater ____.

momentum

Impulses are ___ when an object bounces.

increased

In order to catch a ball, a baseball player extends the hand forward before impact with the ball and then lets it ride backward in the direction of the ball's motion. Doing this reduces the force of impact on the player's hand principally because the ____.

time of impact is increased

When you are in the way of a fast moving object and can't get out of its way, you will suffer a smaller force of impact if you decrease its momentum over a ___.

long time

A car traveling along the highway needs a certain amount of force exerted on it to stop in a certain distance. More stopping force is required when the car has ___.

more mass, more momentum, and less stopping time

A bullet is fired from a gun. The speed of the bullet will be about the same as the speed of the recoiling gun if ____.

the mass of the bullet equals the mass of the gun

Padded dashboards in cars are safer in an accident than non-padded ones because an occupant hitting the dash has ____.

increased time of impact

The force of an apple hitting the ground depends upon ____.

the speed of the apple just before it hits; the time of impact with the ground; and whether or not the apple bounces

Compared to falling on a stone floor, a glass may not break when it falls on a carpeted floor because the ____.

carpet provides a smaller impulse and a longer time

A 4 kg ball has a momentum of 12 kg m/s. What is the ball's speed?

3 m/s

A ball is moving at 3 m/s and has a momentum of 48 kg m/s. What is the ball's mass?

16 kg

A heavy truck and a small car rolling down at the same speed are forced to stop in the same amount of time. Compared to the force that needs to stop the car, the forced needed to stop the truck is ___.

greater

A karate expert executes a swift blow and breaks a cement block with her bare hand. The magnitude of the force experienced by her hand is ____.

identical to the force applied to the block

In an elastic collision, colliding object's rebound without ____.

lasting deformation

You're driving down the highway and a bug spatters into your windshield. This is an example of a ___.

inelastic collision

What kind of quantity is momentum?

vector

Does a moving object have momentum?

yes

impulse unit

F x t

velocity unit

d/t

momentum unit

p

newton

kg x m/s²

speed unit

d/t

What is the momentum of a ten-kilogram ball rolling at three meters per second?

30 kg x m/s

What impulse occurs when an average force of 100 newtons acts on a car for 3 seconds?

300 kg x m/s

If you push for half an hour or a whole hour against a stationary wall how much work is done?

no work is done in either case

If you push an object twice as far while applying the same force, how much work do you do?

twice as much work

If you push an object a given distance, while applying twice the force how much work is done?

twice as much work

If you do work on an object in 1/3 the usual time, your power output is ___.

3 times the usual power output

The power required to exert 1 N of force, over a distance of 1 m in 1 second is ___.

1 W

If an object is raised twice as high, its potential energy will be ___.

twice as much

An object lifted 10 meters gains 200 J of potential energy. If the same object is lifted 20 meters its potential energy gain is ____.

twice as much

A 1000-kg car and a 2000-kg car are hoisted the same distance. Raising the more massive car requires ___.

twice as much work

An object that has kinetic energy must be ____.

moving

An object may have potential energy because of its ___.

location

A bow is drawn so that it has 40 J of potential energy. When fired, the arrow will ideally have a kinetic energy that is ___.

40 J

When a car is braked to a stop, its kinetic energy is transformed into ___.

potential energy

After rolling halfway down an incline, a marble's kinetic energy is ____.

the same as its potential energy

The ball rolling down an incline has its maximum potential energy at ___.

the top

Neglecting friction, a small ball; and a similar large ball, at rest, are allowed to roll down and incline for only one second. At this instance, the large ball will have a greater ____.

potential energy; kinetic energy; and speed

What tasks requires the most work: lifting a 50-kg sack 2 meters or lifting a 25-kg sack 4 meters?

they are the same

Both a 50-kg sack is lifted 2 meters from the ground and a 25-kg sack is lifted 4 meters in the same time. The power exerted in raising the 50-kg sack is ___.

the same

A 2-kg mass is held 4 m above the ground. What is the approximate potential energy of the mass with respect to the ground?

80 J

Using 1000 J of work, a toy elevator is raised from the ground floor to the second floor in 20 seconds. The power needed to do this job is ____.

50 W

What is the potential energy of a 100 rock that is sitting on a hill 300 meters high?

30,000 J

What is the kinetic energy of a bicycle with a mass of 14 kg traveling at a velocity of 3 m/s?

63 J

How much power is used if a force of 35 N is used to push a box a distance of 10 m in 5 seconds?

70 W

A book weighing 1 N is lifted 2 m. How much work was done on the book?

2 J

tangential speed

the linear speed of an object moving in a circular path

rotational speed

sometimes called angular speed; involves the # of rotations or revolutions per unit of time

torque

the product of force and lever-arm distance, which tends to produce rotation

rotational inertia

the property of an object that measures its resistance to 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

center of mass (CM)

the average position of the mass of an object; 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

equilibrium

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

centripetal force

a force directed toward a fixed point, usually the cause of circular motion means "center seeking" or "toward the center"

centrifugal force

an outward force apparent in rotation frame of reference. It is apparent in the sense that it is not part of an interaction but as a result of rotation-- which no reaction-force counterpart

angular momentum

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

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 or no torques to the angular momentum after the event

name the action and reaction: a hammer hits a nail

action: hammer hitting nail
reaction: nail resisting hammer

name the action and reaction: earth's gravity pulls down on a book

action: earth's gravity pulls down on book
reaction: book pulling earth towards it

name the action and reaction: a helicopter blade pushes air downward

action: helicopter blade pushes air downward
reaction: air pulls blade toward it

name the action and reaction: you step off of a curb

action: earth pulling your down
reaction: the ground pulling towards you

name the action and reaction: you pat your little sister on the back

action: you pat your little sister on the back
reaction: your sister's back pushes back on your hand

name the action and reaction: a wave hits the shore

action: a wave hits the shore
reaction: the shore pushes the wave back

name the action and reaction: a baseball bat hits a baseball

action: a baseball bat hits a baseball
reaction: baseball pushes back on the baseball bat

When you push against the wall with your fingers, they bend because the experience a force. Identity this force.

Reaction (action-reaction)

How many forces are required for an interaction?

two

kinetic

energy of motion

centripetal

type of force that keeps objects moving in a circle

mass

amount of matter in an object

acceleration

rate at which velocity changes over time

velocity

speed in a given direction

weight

amount of force exerted on an object due to gravity

gravity

attractive force between two objects

inertia

tendency of a moving object to keep moving

speed

distance covered per unit of time

momentum

depends on the mass and velocity of an object

newton

unit of measurement for force

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