Chapter 2: Motion

The "weightlessness" of a skydiver or astronaut is really _____

a lack of perception of weight because everything around the person is falling with the person.

A newton is____

a unit of force; equal to 1 kg x m/s^2

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

acceleration

The velocity attained by a falling object depends on ______

air resistance and how far it falls

Forces...

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

For a measurement of motion to be meaningful, or even possible, it must _____

consider the motion of an object compared to something else that is not moving.

Speed is equal to...

distance traveled divided by time taken

acceleration

feet per second squared

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

force

The impasse (change in momentum) an object experiences is greater when the ____ and ___ are greater.

force applied to the object; time of application.

Aristotle believed rolling objects tend to slow down and stop because the natural state was to be at rest. In reality, rolling objects slow down and stop because of the force of ______

friction

Galileo was more successful than Aristotle in correctly understanding the nature of force and inertia because ____

he performed most rigorous and logical experiments.

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

What is a measurement of how much inertia an object has and also is a measurement of how much matter is in something?

mass

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

mass and force

position

meters

speed

miles per hour (mph)

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 conservation of momentum...

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

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

speed; direction

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

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

third

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

velocity; force

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

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

inertia

Newton's first law of motion, is primarily related to the idea of ____

inertia

The weight of an object ______

is fond by w = mg, where g is the acceleration of gravity; is the force of gravity pulling on it; in metric units is measured in newtons

Ancient scientists such as Aristotle developed incorrect theories about the nature of motion and forces because ______

it seemed contrary to everyday experience to expect objects to keep moving unless acted on; they did not properly understand friction or gravity

velocity (measurement)

km/s to the north

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

False

True or False: 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

One newton is equal to _____

1 kg x m/s^2

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

1.5 seconds (twice as long)

Two identical planets orbit a star. One is four times as far from the star as the other. The more distant planet experiences ____ as much gravitational force from the star as the closer planet.

1/16

What is the approximate orbital period of a geosynchronous satellite?

24 hours

With a normal load of passengers, a ferris wheel has a total mass of m. Spinning it at velocity v requires a centripetal force F. If the wheel were spun twice as fast, the force required would be _____.

4F

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

A change in its position over a period of time.

Which condition is necessary for a satellite to orbit the Earth?

It must "fall" at the correct rate compared to its "horizontal" motion.

Newton's Second Law of Motion

The acceleration of an object is proportional to the force applied and inversely proportional to the mass of the object.

Newton's Third Law of Motion

Any force exerted on an object from something else is paired with an equal and opposite force exerted by the object on something else.

When a dart gun fires a dart, Newton's third law (equation) applies: There is an equal force on the gun backward as on the dart forward. Why does the dart move faster than the gun recoils?

Because of Newton's second law. The forces are equal but the masses are not, so the less massive object has a bigger acceleration.

Friction____

Must be balanced if an object moves at a constant velocity, always acts in a direction opposite motion, and is a force.

The idea that a force exists between two bodies and depends on the product of their masses and the square of the distance between them is _______ universal law of _______.

Newton's; gravity

What are the steps required to make measurement of a moving object?

Note the position of the moving object at different times and establish a reference object that is stationary.

Newton's First Law of Motion

Objects remain in a state of rest or a state of motion unless acted on by an unbalanced force.

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 experiences forces; why does only one accelerate?

Only one car experiences an unbalanced (net) force.

instantaneous speed

The rate of change of position over an infinitesimally small time interval.

velocity

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

constant speed

The state of covering equal distances in exactly equal periods of time.

average speed

The value of distance traveled/total time for an object for a relatively long total time.

True of False: The motion of an object will only change in some way if it experiences a net force.

True