# Physics Chapters 3 & 4

Consider drops of water leaking from a water faucet. As the drops fall they

get farther apart

An object following a straight line path at constant speed

has zero acceleration

One object has twice as much mass as another object. The first object also has twice as much

inertia

When you look at the speedometer in a moving car, you see the car's

instantaneous speed

When a basketball player jumps to make a shot, once the feet are off the floor, the jumper's acceleration

is g; no more, no less

The hang time (time one's feet are off the ground in a jump) for most athletes is

less than 1 second

One possible unit of speed is

miles per hour, light years per century and kilometers per hour

Friction is a force that always acts

opposite to an object's motion

If you drop a feather and a coin at the time in a tube filled with air, which will reach the bottom of the tube first?

the coin

A sheet of paper can be withdrawn from under a container of milk without toppling it if the paper is jerked quickly. The reason this can be done is that

the milk carton has inertia

An object weighs 30 N on Earth. A second object weighs 30 N on the moon. Which has the greater mass?

the one on the moon

Acceleration is defined as

the rate at which velocity changes itslef

Compared to its mass on Earth, the mass of a 10 kg object on the moon is

the same

Galileo found that a ball rolling down one inclined plane would roll how far up another inclined plane?

to nearly its original height

A force can simply be defined as a push or a pull.

true

An astronaut has the same mass of Earth as in space

true

Even though a car is slowing down, it is still accelerating in the most general definition of acceleration.

true

Friction refers to the force between two surfaces that are sliding past each other.

true

Inertia is the property that every material object has; inertia resists changes in an object's state of motion.

true

The rate at which distance is covered is called speed.

true

The rate at which velocity changes with time is called acceleration.

true

The reason a penny thrown straight up inside an airplane will come back to your hand is that you, the air inside the plane, and the penny are all moving at the same horizontal velocity.

true

Velocity is different from speed in that velocity is speed in a given direction.

true

When we discuss the motion of something, its motion is described relative to something else.

true

How much does a 3.0 kg bag of bolts weigh?

29.4 N

Suppose a car is moving in a straight line and steadily increases its speed. It moves from 35 km/h to 40 km/h the first second and from 40 km/h to 45 km/h the next second. What is the car's acceleration?

5 km/h x s

Suppose a jumper claims a hang time of 2 seconds. Then that jumper must be able to jump a vertical distance of

5 m

A car starts from rest and after 7 seconds it is moving at 42m/s. What is the car's average acceleration?

6m/s squared

A ball is thrown upwards and caught when it comes back down. In the absence of air resistance, the speed of the ball when caught would be

more than the speed it had when thrown upwards

A ball is thrown straight up. At the top of its path its instantaneous speed is

0 m/s

A train travels 6 meters in the first second of travel, 6 meters again during the second second of travel and 6 meters again during the third second. Its acceleration is

0 m/s squared

The vertical height attained by a basketball player who achieves a hang time of a full one second is about

1.2 m

A freely falling object starts from rest. After falling for 1 second, it will have a speed of about

10 m/s

A car accelerates at 2 m/s. Assuming the car starts from rest, how much time does it need to accelerate to a speed of 20 m/s?

10 seconds

The mass of a lamb that weighs 110 N is about

11 kg

If a projectile is fired straight up at a speed of 30 m/s, the total time to return to its starting point is about

6 seconds

Suppose you take a trip that covers 180 km and takes 3 hours to make. Your average speed is

60 km/h

A freely falling object starts from rest. After falling for 6 seconds, it will have a speed of about

60 m/s

A bag of sports equipment has a mass of 10.0 kilograms and a weight of

98 N

Suppose an object is in free fall. Each second the object falls

a larger distance than in the second before

Speed is.......

a measure of how fast something is moving, always measured in terms of a unit of distance divided by a unit of time and the distance covered per unit time

If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each second by

about 10 m/s

A ball is thrown straight up. At the top of its path its acceleration is

about 10 m/s squared

When something falls to the ground, it accelerates. This acceleration is called the acceleration due to gravity and is symbolized by the letter g. What is the value of g on Earth's surface?

about 10 m/s squared

In the absence of air resistance, objects fall at constant

acceleration

The law of inertia applies to

both moving and nonmoving objects

Friction

come from microscopic bumps that act as obstructions to the object's motion, is the name given to the force acting between surfaces sliding past one another, acts in a direction that opposes the motion of an object

A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. During this time the acceleration of the ball is always

directly downward

A ball is thrown into the air. At the highest point, the ball has zero velocity and zero acceleration.

false

As a ball falls freely, the distance it falls each second is the same.

false

Average speed is defined as the time it takes for a trip divided by the distance.

false

If a hockey puck were to slide on a perfectly frictionless surface, it will eventually slow down because of its inertia

false

The SI unit of force is the kilogram.

false

The SI unit of mass is the newton.

false

The force due to gravity acting on an object is its mass.

false

The name of the astronomer who first publicly stated that Earth revolved around the sun is Galileo.

false

When a car rounds a corner at a constant speed, its acceleration is zero

false

As an object falls freely in a vacuum, its

velocity increases

The law of inertia states that an object

will continue moving at the same velocity unless an outside force acts on it, will continue moving in a straight line unless an outside force acts on it, that is not moving will never move unless a force acts on it and at rest will remain at rest unless acted on by an outside force

After a cannonball is fired into frictionless space, the amount of force needed to keep it going equals

zero, since no force is necessary to keep it moving