Physics Exam- 3&4
a pencil lays on your desk. If the earth is moving around the sun at a speed of 30 km/s, how fast is the pencil moving relative to the desk? How fast is the pencil moving relative to the sun?
0 km/s; 30 km/s
A ball is thrown straight up. At the top of its path, its instantaneous speed is
0m/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
0m/s2
A car accelerates at 2m/s^2. assuming the car starts from rest, how much time does it need to accelerate to a speed of 20 m/s?
10 seconds
A ball is thrown straight up. At the top of its path, its acceleration is
10m/s2
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.s
Suppose you take a trip that covers 180 km and takes 3 hours to make. Your average speed is
60 km/h
A bag of sports equipment has a mass of 10.0 kg and a weight of
9.8 N
If a ball were equipped with a speedometer and allowed to freely fall on a planet where the acceleration due to gravity is 23 m/s^2, the reading on the speedometer would increase each second by
A rate that depends on its initial speed
If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each second by
About 10 m/s
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^2
One possible unit of speed is
miles per hour light years per century kilometer per hour
If the force of gravity suddenly stopped acting on the planets, they would
move in a straight line tangent to their orbits
Consider drops of water leaking from a water faucet. As the drops fall, they...
remain at a relatively fixed distance from each other
You would have the largest mass of gold if your chunk of gold weighed 1 N on
the moon
Unit of velocity is the meter
False
a ball is thrown into the air. at the highest point, the ball has zero velocity and zero acceleration
False
a unit of acceleration is meters per second
False
an astronaut weighs the same on Earth as in space
False
as a ball falls freely, the distance it falls each second it 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
if you were to slide a hockey puck across a frictionless ice rink, there must be a horizontal force on it to keep it in motion
False
the SI unit of mass is the newton
False
the amount of matter in an object is its weight
False
unless stated otherwise, when we discuss the speeds of things, we mean with respect to the center of the universe
False
when a car rounds a corner at a constant speed, its acceleration is zero
False
Friction
comes 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
Compared to its mass on Earth, the mass of a 10-kg object on the moon is
the same
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...
the same as the speed it had when thrown upwards
Suppose an object is in free fall. Each second the object falls...
the same distance as in the second before
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 can see the car's...
instantaneous speed
if a projectile is fired straight up at a speed of 10 m/s , the total time to return to its starting point is about
2 seconds
You and a friend are jumping on a trampoline. Why does Earth, which is rapidly orbiting around the sun, not move under your feet when you jump?
Newton's first law holds that your body moves along with Earth because it is not compelled to change its motion by an unbalanced force
Friction is a force that always acts..
Opposite to an objects motion
an astronaut has the same mass on 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
in the fourth century B.C., Aristotle divided motion into 2 types: natural motion and violent 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
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
Which of the following is NOT true about Aristotle's concept of violent motion?
Violent motion is thought to be either straight up or straight down
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 the distance covered per unit of time
In the absence of air resistance, object fall at constant...
acceleration
Acceleration is defined as the CHANGE in
velocity divided by the time interval
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 at rest will remain at rest unless acted on by an outside force
Suppose you are in a car that is going around a curve. The speedometer reads a constant 30 miles per hour. Which of the following is NOT true?
your velocity is constant
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
