chapter 2 Physical Science

Two cars drive down a hill. One applies its brakes and moves at a constant speed; the other doesn't and increases in speed all the way down. Both cars experience forces; why does only one accelerate?

Only one car experiences an unbalanced (net) force.

Select the properties or quantities that you must measure to establish that something is moving. (Choose all that apply.)

Position Time

Arrange the quantities in order so that each term is a measurement of the rate of change of the term above it.

Position Velocity Acceleration

Change in the motion of an object is an acceleration. Such a change will result in a different ______ or ______ or both.

Speed Direction

Velocity is the ______ and ______ of a moving object. (Select two.)

Speed Direction

Select the four fundamental forces.

Strong nuclear Electromagnetic Gravity Weak

Select all the cases in which an object undergoes acceleration.

The Moon orbits the Earth. A leaf falls from a tree. A car brakes and slows down.

What causes the total (net) momentum of a group of objects to change?

The action of an outside force

A bat hits a ball. The bat exerts a force, F, on the ball. Which statement is true?

The ball exerts a force, F, on the bat.

In a car crash, the momentum of the moving car changes as the car stops (an impulse is applied by the object the car hits). The best way to reduce the amount of force during the impact is to ______.

increase the length of time of the collision itself

Newton's first law of motion, that objects continue to move (or remain stationary) unless acted on by an unbalanced force, is primarily related to the idea of ______.

inertia

The tendency of a body at rest to remain at rest and of a body moving in a straight line to remain moving in a straight line is defined as ______.

inertia

Forces ______.

are a push or pull on an object result in no change in motion when balanced can change the motion of an object

The distance covered in a specific amount of time is better known as ______________.

speed

The graph shows _____________ changing at a constant rate of 5 km/h per _____________.

speed second

You will change the motion of an object if you change its __________.

speed, velocity, or direction

One newton is equal to ______.

1 kg⋅m s2

The mass of an object determines how much inertia it has. Rank the following objects from the least massive (top) to the most massive (bottom).

1. A leaf falling from a tree 2. A laptop computer floating freely inside the International Space Station 3.A car driving at highway speeds 4.A house

1. Newton's first law 2. Newton's second law 3. Newton's third law

1. Objects remain in a state of rest or a state of motion unless acted on by an unbalanced force. 2. The acceleration of an object is proportional to the force applied and inversely proportional to the mass of the object. 3. Any force exerted on an object from something else is paired with an equal and opposite force exerted by the object on something else.

1. Vf 2. /v 3. a

1. at + vi 2. vf + vi 2 3. vf − vi t

1. Newton's first law 2. Newton's second law 3. Newton's third law

1. v = constant 2. F = m × a 3. FA due to B = FB due to A

1. D= 2. /v= 3. A=

1. v × t 2. Δd t 3. Δv t

A penny dropped from a one-story building takes about 0.75 s to fall to the ground. How long would it take to fall if dropped off a four-story building?

1.5 s (twice as long)

1.Position 2.Speed 3.Velocity 4.Acceleration

1.Meters 2.Miles per hour (mph) 3.Km/s to the north 4.Feet per second squared (ft/s2)

Impulse Acceleration Momentum Velocity Inertia

A change in momentum A change in velocity A quantity involving the inertia and velocity of an object A change in position The resistance of an object to motion

The rate of change of velocity per unit time is

Acceleration

In Newton's second law, force has a relationship with which two variables?

Acceleration Mass

"Whenever two objects interact, the force exerted on one object is equal in size and opposite in direction to the force exerted on the other object." This is a statement of ______ of motion.

Newton's third law

If we consider an object falling in a vacuum, such as a meteor falling to impact the Moon, there is only a single force involved.

False Rationale: There are always equal and opposite forces whenever a force acts. In the example, the Moon exerts a force on the meteor, but the meteor exerts an equal and opposite force on the Moon. Since the meteor is much less massive, it experiences a much larger acceleration.

Which two fundamental forces are we most familiar with through everyday experience?

Gravity and electromagnetism

In the absence of any forces, what keeps an object moving at constant speed?

Inertia

Centripetal force Centrifugal force

It acts toward the center of the orbit. It appears to act toward the outside of the orbit.

Select all the true statements about the football's motion.

It would be easiest to calculate it by considering the vertical and horizontal components separately. It advances sideways in equal amounts because it has a constant horizontal velocity.

Weight Mass

Measured in newtons or pounds Measured in kilograms

Two identical cars approach each other at 30 mph. Prior to colliding, one driver hits the brakes so that his car's speed drops to 5 mph. Considering the conservation of momentum, which statement is true?

The momentum of the system changed before the collision.

________________ is the speed and direction of a moving object, such as 10 km/h to the west.

Velocity

Select all the choices that are correct representations of acceleration, which is the change in velocity per unit time. (Here t is the length of time during which the acceleration occurs.)

a = 12m/s−10m/s 2s a = Δv t a = vf−vi t

In the most basic analysis, motion of an object is inferred by measuring ______.

a change in its position over a period of time

A newton is ______.

a unit of force equal to 1 kg⋅ms 2

The ratio of change in velocity to time elapsed is ______.

acceleration

The velocity attained by a falling object depends on _______.

air resistance how far it falls

Friction ______.

always acts in a direction opposite motion is a force must be balanced if an object moves at a constant velocity

Net force ______.

can be larger or smaller than each individual force, depending on the directions they are acting in is the overall effect of all the forces acting on an object

A ball is being swung on a string. Vector A indicates the ___________ force on the ball.

centripetal

Speed is equal to ______.

distance traveled divided by time taken Rationale: Speed = d/t

The momentum of a rocket launched into space is ______.

equal to but in the opposite direction of the exhaust momentum

The Moon orbits the Earth in a circular path because of inertia.

false

A(n) ______________ is any push or pull on an object.

force

A ball is being swung on a string. The arrow pointing along the string (A) represents the ______.

force on the ball from the string

Aside from air resistance, the most important factor in determining the velocity of a falling object is _______. (Assume the object is falling on Earth.)

how much time it spends falling

A change in the momentum of an object caused by exerting a force on it for a period of time t is called a(n)

impulse

______________ is a measurement of how much inertia an object has. It is also a measurement of how much matter is in something.

mass

In Newton's second law, acceleration is related to which two properties?

mass force

The conservation of momentum ______.

means that the momentum of a group of objects cannot change unless external forces act requires that an object will not change velocity unless acted on by an outside force

p=mv The equation shown represents

momentum

If an object is acted on by many forces, the resulting acceleration will be the same as if there is one _______________ force, which is the sum of all the forces.

net

The slope of the graph shown ______. (Select all that apply.)

represents the acceleration of the object shows a rate of change indicates a constant acceleration

A bullet is fired straight up. Neglecting air resistance, the speed of the bullet when it falls back down is ______.

the same as when it came out of the gun

For a freely falling object dropped from rest, the distance it falls is proportional to _______.

the square of the time spent falling Rationale: d = 1/2 at2.

The arrow maintains a constant horizontal velocity while its vertical velocity increases steadily because ______.

there are no forces in the horizontal direction

Newton's _________________ law of motion is that two interacting bodies produce a pair of equal and opposite forces.

third

The impulse (change in momentum) an object experiences is greater when the ______ and ______ are greater. (Select two.)

time of application force applied to the object

The variable-length vertical arrows in the figure represent the changing _____ of the projectiles.

velocity

Momentum (p) is the product of an object's ______ and ______.

velocity mass

Newton's law of inertia states that a moving body maintains a constant ____________ unless a __________ acts on it.

velocity or state force

Compared to being on Earth, on Mars your ______.

weight would be different and your mass the same