Chapter 12

Free fall is the motion of an object resulting from _______________.

gravity

One newton is the force that can give a mass of 1 kg an acceleration of ________________.

1 m/s2

A force of 6.2 X 105 N is needed to blast off a 5.0 X 103 kg rocket from rest. What is the rocket's average acceleration?

124 m/s2 (620,000 kg • m/s2 divided by 5,000 kg)

An object changes its motion only if a force acts on it to change its speed or direction. This is a statement of Newton's _____________.

1st law

What unbalanced force is needed to give a 976 kg vehicle acceleration of 2.50 m/s2?

2.44 x 103 N

What is the momentum of 255 g apple falling at 16.0 m/s? (hint: convert g to kg)

4.08 kg • m/s downward

Calculate the velocity of a 90.5 kg man running south with a momentum of 389 kg x m/s.

4.30 m/s south

A 0.25 kg steel ball experiences a net force of 1.15 N as it rolls down a ramp. What is the acceleration of the ball?

4.6 m/s2

Which of the following will result in the greatest acceleration?

56 N acting on a 1-kg box

How much does a 59.0 kg woman weigh on Earth? What is her "scientific" weight?

578 N

A 10.0 kg dog chasing a rabbit north at 6.0 m/s has a momentum of __________________.

60.0 kg • m/s north

A force of 240.0 N causes an object to accelerate at 3.2 m/s2. What is the mass of the object?

75 kg

The value for the acceleration of objects in free fall near Earth is _______.

9.8 m/s2

Which statement about weight is incorrect?

An object weighs more on the moon than it weighs on Earth

Near Earth's surface, the strongest gravitational force would occur between an elephant and ___________.

Earth

A force is continuously applied to an object, causing it to accelerate. After a period of time, however, the object stops accelerating. What conclusions can be drawn?

The object is experiencing some kind of friction. (friction opposes motion)

Rearrange the equation for Newton's second law of motion to define acceleration in terms of force and mass.

a = f/m; acceleration = force divided by mass

Which object has the greatest inertia?

a bowling bowl

Which is an example of projectile motion?

a dart thrown at a dart board

Which of the following has a momentum of zero?

a newspaper lying on a table

Which object does not have momentum?

a rock by the side of the road

Which of the following is not a factor in calculating momentum?

acceleration

Which of the following objects exerts a gravitational force?

all of the above (a bowling ball, a book, a feather)

Which statement illustrates Newton's first law?

all of the above (a stone will not move unless something pushes or pulls it, a ball rolling across the floor eventually slows down, as a car comes to a stop, the passengers continue to move forward)

Which of the following is true?

all of the above (weight and mass are proportional but not equal, weight is the gravitational force on object experiences due to its mass, the weight of an object on Earth is greater than the weight of the same object on the moon, but the object's mass stays the same.

Whenever an object is standing still, which value is always zero?

all of the above; (speed, velocity, and momentum)

If the net force on an object is zero, then the object has _____________.

balanced forces

Two identical cars are traveling at equal speeds. One is going north and the other south. If they collide head-on and stick together, what will happen to the motion of the cars?

both cars will stop

The free fall acceleration of an object under Earth's gravity is directed toward the _______________.

center of the earth

Terminal velocity is defined as _____________________________________________________.

constant velocity reached by a falling object when air resistance equals gravity

When objects are moved further apart from each other, the force of gravity between them ____________.

decreases

The gravitational force between two objects depends on masses of objects and ___________________.

distance between objects

When you kick a stone, you foot exerts a force on the stone, and the stone exerts a force ___________ in size and __________ in direction on your foot.

equal; opposite

Whenever a force is exerted, another force occurs that is ________ in size, and ________ in direction.

equal; opposite

When the velocity of an object changes, it is acted upon by a(n) _______.

force

Orbital motion is a combination of ____________ motion and free fall (free fall is vertical)

forward

Orbital motion is a combination of ___________________.

forward motion and free fall

When a satelitte orbits Earth, it experiences two motions: ___________ motion and __________ toward Earth.

forward; free fall

the motion of a body when only the force of gravity is acting in the body

free fall

The weight of an object can be calculated by multiplying mass by _____________________.

free-fall acceleration

What force causes a skater sliding on the ice to gradually slow down?

friction

When an object is in free fall, the only force acting on it is _______________.

gravity

Astronauts "float" when inside an orbiting spaceship because they are _______________.

in free fall

The gravitational force on an object ___________ as the object's mass increases.

increases

the tendency of an object to resist a change in motion unless an outside force acts on the object

inertia

The tendency of an object at rest to remain at rest is __________.

inertia (newton's 1st law)

Free-fall acceleration near Earth's surface _____________________________.

is the same for all objects

When a moving bowling ball hits pin, some of the ball's momentum ____________________.

is transferred to the pin

How does the total momentum of two objects before a collision compare with the total momentum after the collision?

it is the same

Which of the following units is used to measure acceleration?

m/s2

If you divide momentum by velocity, the result is the value of the object's _______.

mass

Increasing which of these conditions results in more gravitational force between two objects?

mass

An object's momentum is determined by the object's ___________________.

mass and velocity

According to Newton's second law of motion, force is the product of _______ and ______________.

mass; acceleration

a quality defined as the product of the mass and velocity of an object

momentum

All ___________ objects have momentum.

moving

The SI unit of force, named after the scientist who described the relationship between motion and force, is called the ____________.

newton

Near Earth's surface, an object's free-fall acceleration increases as its _________________.

none of the above (mass increases, speed increases, weight increases)

The path of a pitched ball is an example of ______________ motion.

projectile

the curved path that an object follows when thrown, launched, or otherwise projected near the surface of the Earth; the motion of objects that are moving in two dimensions under the influence of gravity

projectile motion

The force exerted on the racket by a hit tennis ball is the __________________.

reaction force

When air resistance balances the weight of a falling object, the velocity _______________.

remains constant

Action and reaction forces always occur at the _______ time.

same

An important safety feature in your car that is based on the concept of inertia is the ____________________.

seat belt and/or air bag

As the time period of an object's momentum change becomes longer, the force needed to cause this change becomes _____________.

smaller

When gravitational forces and air resistance equalize on an object that is falling toward Earth and the object stops accelerating, its velocity is called the _____________ velocity.

terminal

the constant velocity of a falling object when the force of air resistance is equal in magnitude and opposite in direction to the force of gravity.

terminal velocity

Weight is best described as __________________________________.

the downward force exerted on an object due to gravity

What is the reaction force when you place a cup on a table?

the force of the table on the cup

If an equal force is applied to two cars of equal mass, Car A and Car B, Car A will have ____________________ acceleration as (than) Car B.

the same

If the car you are riding in comes to a sudden stop, _______________ helps stop your forward motion.

the seat belt

Which statement about action-reaction force pairs is incorrect?

they act on the same object

A seat belt helps you when your car stops suddenly by providing a(n) __________________.

unbalanced backward force

An object at rest remains at rest unless it experiences a(n) ____________________.

unbalanced force

A tug-of-war that results in one team pulling the other across the line is _____________.

unbalanced forces

a measure of the gravitational force exerted on an object; its value can change with the location of the object in the universe

weight