Physics Exam
A ball is thrown straight upward at 10 m/s. Ideally (no air resistance), the ball will return to the thrower's hand with a speed of
10 m/s
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/s². Assuming the car starts from rest, how much time does it need to accelerate to a speed of 20 m/s?
10 seconds
In the absence of air resistance, at what other angle will a thrown ball go the same distance as one thrown at an angle of 75 degrees?
15 degrees
A cannonball is launched from the ground at an angle of 30 degrees above the horizontal and a speed of 30 m/s. Ideally (no air resistance) the ball will land on the ground with a speed of
30 m/s
Which best approximates the resultant of a pair of 6-unit vectors at right angles to each other?
8 units
At what part of a path does a projectile have minimum speed?
At the top of its path
If you drop a feather and a coin at the same time in a vacuum tube, which will reach the bottom of the tube first
Neither-they will both reach the bottom at the same time
At the instant a ball is thrown horizontally with a large force, an identical ball is dropped from the same height. Which ball hits the ground first?
Neither. They both hit the ground at the same time
If you drop a feather and a coin at the same time in a tube filled with air, which will reach the bottom of the tube first?
The coin
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
Suppose an object is in free fall. Each second the object falls
a larger distance than in the second before
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/s²
A ball is thrown straight up. At the top of its path its acceleration is
about 10 m/s².
In the absence of air resistance, objects fall at constant
acceleration
In order to find the components of a vector, you should
all of the above
One possible unit of speed is all of the above
all of the above
Speed is
all of the above
When representing velocity as a vector,
all of the above
A ball is thrown into the air at some angle. At the very top of the ball's path, its velocity is
entirely horizontal
A ball is thrown into the air. At the highest point, the ball has zero velocity and zero acceleration.
false
A ball will go the farthest if thrown almost horizontally.
false
A quantity that has both magnitude and direction is called a scalar.
false
A quantity that has only magnitude is called a vector
false
A single vector can be replaced by two vectors in the x- and y-directions that are at right angles to each other. These two x and y vectors are called the resultants of the original vector.
false
A unit of acceleration is meters per second.
false
A unit of velocity is the meter.
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
Mass is a vector quantity.
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
When adding two vectors at right angles, the resultant of the vectors is the algebraic sum of the two vectors.
false
An object is dropped and falls freely to the ground with an acceleration of g. If it is thrown upward at an angle instead, its acceleration would be
g downward
Consider drops of water leaking from a water faucet. As the drops fall they
get farther apart
When you look at the speedometer in a moving car, you can 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
A projectile is fired horizontally in a vacuum. The projectile maintains its horizontal component of speed because it
is not acted on by any horizontal forces
If you could throw a baseball horizontally at a speed of 8 km/s and if there were no air drag and nothing to stop it,
it would orbit Earth
The hang time (time one's feet are off the ground in a jump) for most athletes is
less than 1 second.
A scalar is a quantity that has
magnitude
A vector is a quantity that has
magnitude and direction
An airplane flying into a head wind loses ground speed, and an airplane flying with the wind gains ground speed. If an airplane flies at right angles to the wind, then ground speed is
more.
In Chapter 2, you learned about "hang time," the time a jumper's feet are off the ground in a vertical jump. If the jumper runs horizontally and has the same vertical component of takeoff velocity, hang time will be
no different
Jose can jump vertically 1 meter from his skateboard when it is at rest. When the skateboard is moving horizontally, Jose can jump
no higher
When in orbit, a satellite such as the space shuttle is
simply a projectile
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.
After a rock that is thrown straight up reaches the top of its path and is starting to fall back down, its acceleration is (neglecting air resistance)
the same as when it was at the top of its path
The horizontal component of a projectile's velocity is independent of
the vertical component of its velocity
Any vector can be represented by two other vectors that are at right angles to each other.
true
Even though a car is slowing down, it is still accelerating, in the most general definition of acceleration.
true
The length of a vector represents its magnitude
true
The orientation of a vector shows its direction.
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 vector sum is called the resultant.
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 the motion of something else.
true
Wind velocity can be represented as a vector quantity.
true
Acceleration is defined as the CHANGE in
velocity divided by the time interval
As an object falls freely in a vacuum, its
velocity increases
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/s²
A projectile launched horizontally hits the ground in 0.8 seconds. If it had been launched with a much higher speed in the same direction, it would have hit the ground (neglecting Earth's curvature and air resistance) in
0.8 s
The vertical height attained by a basketball player who achieves a hang time of a full one second is about
1.2 m
If a ball were equipped with a speedometer and allowed to fall freely on a planet where the acceleration due to gravity is 23 m/s², the reading on the speedometer would increase each second by
23 m/s
Suppose a small plane can fly at 170 km/h relative to the surrounding air. Suppose also that there is a 60 km/h tailwind. How fast does the plane's shadow move across the ground?
230 km/h
In the absence of air resistance, the angle at which a thrown ball will go the farthest is
45 degrees
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
A cannonball is fired at some angle into the air. In the first second it moves 5 meters horizontally. Assuming it doesn't hit the ground and air resistance is negligible, how far does it move horizontally in the next second?
5 m
Suppose a jumper claims a hang time of 2 seconds. Then that jumper must be able to jump a vertical distance of
5 m
What is the resultant of a 3-unit vector and 4-unit vector at right angles to each other?
5 units.
A car starts from rest and after 7 seconds it is moving at 42 m/s. What is the car's average acceleration?
6 m/s²
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
A baseball is hurled into the air at an angle of 30 degrees above the horizontal and lands on a target that is at the same level as that where the baseball started. The baseball will also land on the target if it is thrown at an angle of
60 degrees
Suppose you take a trip that covers 180 km and takes 3 hours to make. Your average speed is
60 km/h
A cannonball is launched horizontally from a tower. If the cannon has a barrel velocity of 60 m/s, where will the cannonball be 1 second later? (Neglect air resistance.)
60 m downrange
A freely falling object starts from rest. After falling for 6 seconds, it will have a speed of about
60 m/s
A cannon with a barrel velocity of 140 m/s launches a cannonball horizontally from a tower. Neglecting air resistance, how far vertically will the cannonball have fallen after 4 seconds?
80 m
Which of the following would NOT be considered a projectile?
A cannonball rolling down a slope
A ball thrown in the air will never go as far as physics ideally would predict because
Air friction slows the ball
In the absence of air resistance, the vertical component of a projectile's velocity doesn't change as the projectile moves.
Always false
In the absence of air resistance, the horizontal component of a projectile's velocity doesn't change as the projectile moves.
Always true
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
directed downward
