Physics Exam (w/o elastic & inelastic questions; test 3)
A 35-N bucket of water is lifted vertically 3.0 m and then returned to its original position. How much work did gravity do on the bucket during this process?
0 J
A polar bear starts at the North Pole. It travels 1.0 km south, then 1.0 km east, and then 1.0 km north to return to its starting point. This trip takes 45 min. What was the bear's average speed?
0 km/h
You throw a ball upward with an initial speed of 10 m/s. assuming that there is no air resistance, what is its speed when it returns to you?
10 m/s
When you drop a pebble from height H, it reaches the ground with kinetic energy K if there is no air resistance. From what height should you drop it so it will reach the ground with twice as much kinetic energy?
2 H
When you drop a pebble from height H, it reaches the ground with speed V if there is no air resistance. From what height should you drop it so it will reach the ground with twice speed?
4 H
Which requires more work, increasing a car's speed from 0 mph to 30 mph or from 50 mph to 60 mph?
50 mph to 60 mph
The acceleration of gravity on the Moon is one sixth what it is on Earth. An object of mass 72 kg is taken to the Moon. What is its mass there?
72 kg
A 10 kg rock and a 20 kg rock are dropped at the same time and experience no significant air resistance. If the 10 kg rock falls with acceleration a, what is the acceleration of the 20 kg rock?
A
As shown in the figure, a given force is applied to a rod in several different ways. In which case is the torque about the pivot P due to this force the greatest?
A ( _____↑)
Which of the following situations is impossible?
An object has constant non-zero velocity and changing acceleration.
The figure shows scale drawings of four objects, each of the same mass and uniform thickness, with the mass distributed uniformly. Which one has the greatest moment of inertia when rotated about an axis perpendicular to the plane of the drawing at point P?
B (a wagon wheel)
You and your friend, who weighs the same as you, want to go to the top of the Eiffel Tower. Your friend takes the elevator straight up. You decide to walk up the spiral stairway, taking longer to do so. Compare the gravitational potential energy of you and your friend, after you both reach the top.
Both of you have the same amount of gravitational potential energy at the top
A constant net force acts on an object. Describe the motion of the object.
Constant acceleration
Five forces act on a rod that is free to pivot at point P, as shown in the figure. Which of these forces is producing a counter-clockwise torque about point P?
Force C ↙
When an object experiences uniform circular motion, the direction of the acceleration is
Is directed toward the center of the circular path
An object moving in the +x direction experiences an acceleration of +2.0 m/s^2. This means the object
Is increasing its velocity by 2.0m/s every second
A spaceship is traveling to the Moon. At what point is it beyond the pull of Earth's gravity?
It is never beyond the pull of Earth's gravity
Two children, Ahmed and Jacques, ride on a merry-go-round. Ahmed is at a greater distance from the axis of rotation than Jacques. Which of the following are true statements? (There could be more than one correct choice.)
Jacques and Ahmed have the same angular speed. Ahmed has a greater tangential speed than Jacques.
James and John dive from an overhang into the lake below. James simply drops straight down from the edge. John takes a running start and jumps with an initial horizontal velocity of 25 m/s. Compare the time it takes each to reach the lake below if there is no air resistance.
James and John will reach the surface of the lake at the same time
In the absence of an external force, a moving object will
Move with constant velocity
Who has a greater weight to mass ratio, a person weighing 400 N or a person weighing 600 N?
Neither; their ratios are the same
If you blow up a balloon, and then release it, the balloon will fly away. This is an illustration of
Newton's third law
Two cars collide head-on. At every moment during the collision, the magnitude of the force the first car exerts on the second is exactly equal to the magnitude of the force the second car exerts on the first. This is an example of
Newton's third law
When is the angular momentum of a system constant?
Only when no net external torque acts on the system.
A 10 kg rock and a 20 kg rock are dropped from the same height and experience no significant air resistance. If it takes the 20 kg rock a time T to reach the ground, what time will it take the 10 kg rock to reach the ground?
T
Which one has larger kinetic energy: a 500-kg object moving at 40 m/s or a 1000-kg object moving at 20 m/s?
The 500-kg object
Two cyclists who weigh the same and have identical bicycles ride up the same mountain, both starting at the same time. Joe rides straight up the mountain, and Bob rides up the longer road that has a lower grade. Joe gets to the top before Bob. Ignoring friction and wind resistance, which one of the following statements is true?
The amount of work does by Joe is equal to the amount of work done by Bob, but the average power exerted by Joe is greater than that of Bob.
Suppose that an object travels from one point in space to another. Make a comparison between the displacement and the distance traveled.
The displacement is either less than or equal to the distance traveled
Which of Newton's laws best explains why motorists should buckle-up?
The first law
A 20-ton truck collides with a 1500-lb car and causes a lot of damage to the car. Since a lot of damage is done on the car
The force on the truck is equal to the force on the car
Consider two less-than-desirable options. In the first you are driving 30 mph and crash head-on into an identical car also going 30 mph. In the second option you are driving 30 mph and crash head-on into a stationary brick wall. In neither case does your car bounce back from the thing it hits, and the collision time is the same in both cases. Which of these two situations would result in the greater impact force on your car?
The force would be the same in both cases.
An object of mass m sits on a flat table. The Earth pulls on this object with force mg, which we will call the action force. What is the reaction force?
The object pulling upward on the Earth with force mg
A small car meshes with a large truck in a head on collision. which of the following statements concerning the magnitude of the momentum change during the collision is correct?
The small car and the truck experience the same magnitude momentum change
Brick A is dropped from the top of a building. Brick B is thrown straight down from the same building, and neither one experiences appreciable air resistance. Which statement about their accelerations is correct?
The two bricks have exactly the same acceleration
If the force on an object is in the negative direction, the work it does on the object must be negative.
The work could be either positive or negative direction, depending on the direction the object moves.
You are standing in a moving bus, facing forward, and you suddenly fall forward as the bus comes to an immediate stop. What force caused you to fall forward?
There is not a force leading to your fall
Three cars, car X, car Y, and car Z, begin accelerating from rest at the same time. Car X is more massive than car Y, which is more massive than car Z. The net accelerating force exerted on each car is identical. After 10 seconds, which car has the most amount of momentum?
They all have the same amount of momentum
A car goes around a curve of radius r at a constant speed v. What is the direction of the net force on the car?
Toward the curve's center
Consider a car that travels between points A and B. The car's average speed can be greater than the magnitude of its average velocity, but the magnitude of its average velocity can never be greater than its average speed. (T or F)
True
When is the average velocity of an object equal to the instantaneous velocity?
When the velocity is constant
A net force F accelerates a mass m with an acceleration a. If the same net force is applied to mass 2m, then the acceleration will be
a/2
Suppose you try loosening a nut with a wrench, and the nut doesn't give at all. You increase your chance of success if you
all of the above
If the answer to your calculation has units of kg * m^2/s, what type of quantity could it be? (There could be more than one correct choice.)
angular momentum
A pilot drops a package from a plane flying horizontally at a constant speed. Neglecting air resistance, when the package hits the ground the horizontal location of the plane will
be directly over the package
Two displacement vectors have magnitudes of 5 m and 7 m, respectively. When these two vectors are added, the magnitude of the sum
could be as small as 2.0 m or as large as 12 m
As a rocket moves away from the Earth's surface, the rocket's weight
decreases
In a game of pool, the white cue ball hits the #5 ball and stops, while the #5 ball moves away with the same velocity as the cue ball had originally. Both balls have the same mass. This type of collision is
elastic
A stone is thrown straight up. At the top of its path, the net force acting on it is
equal to its weight
A golf club hits a golf ball with force of 2400N. the golf ball hits the club with a force
exactly 2400N
An object of mass m is hanging by a string from the ceiling of an elevator. The elevator is moving up at constant speed. What is the tension in the string?
exactly mg
In an inelastic collision involving an isolated system, the final total momentum is
exactly the same as the initial momentum
A stone is held at a height h above the ground. A second stone with four times the mass of the first one is held at the same height. the gravitational potential energy of the second stone compared to that of the first stone is
four times as much
List the four fundamental forces in nature
gravitational, electromagnetic, strong nuclear, weak nuclear
A 10 kg rock and a 20 kg rock are thrown upward with the same initial speed v(o) and experience no significant air resistance. If the 10 kg rock reaches a maximum height h, what maximum height will the 20 mg ball reach?
h
A person sits on a freely spinning lab stool that has no friction in its axle. When this person extends her arms,
her moment of inertia increases and her angular speed increases
The momentum of an isolated system is conserved
in both elastic and inelastic collisions
The speed of Haley's Comet, while traveling in its elliptical orbit around the Sun,
increases as it nears the Sun
For general projectile motion with no air resistance, the horizontal component of a projectile's acceleration
is always zero
You throw a ball straight up into the air. After it leaves your hand, at what point in its flight does it have the maximum value of acceleration?
its acceleration is constant everywhere
Suppose that a car traveling to the east (+x direction) begins to slow down as it approaches a traffic light. Which statement concerning its acceleration must be correct?
its acceleration is in the -x direction
Suppose that a car traveling to the west begins to slow down as it approaches a traffic light. Which of the following statements about its acceleration is correct?
its acceleration is positive
You drive 6 km at 50 km/h and then another 6 km at 90 km/h. Your avg speed over 12 km drive will be
less than 70 km/h
The acceleration due to gravity is lower on the Moon than on Earth. Which of the following is true about the mass and weight of an astronaut on the Moon's surface, compared to Earth?
mass is same, weight is less
Does the displacement of an object depend on the specific location of the origin of the coordinate system?
no
If the average velocity is non-zero over some time interval, does this mean that the instantaneous velocity is never zero during the same interval?
no
If the position of a car is zero, does its speed have to be zero?
no
If the units of your answer are kg x m^2/s^3, which of the following types of quantities could your answer be?
power
For general projectile motion with no air resistance, the horizontal component of a projectile's velocity
remains a non-zero constant
For general projectile motion with no air resistance, the vertical component of a projectile's acceleration
remains a non-zero constant
A rubber ball and a lump of clay have equal mass. They are thrown with equal speed against a wall. the ball bounces back with nearly the same speed with which it hit. the clay sticks to the wall Which one of these objects experiences the greater momentum change?
the ball
A brick and a feather fall to the earth at their respective terminal velocities. Which object experiences the greater force of air friction?
the brick
In a collision between two unequal masses, which mass receives a greater magnitude impulse?
they receive equal impulses
You are standing in a moving bus, facing forward, and you suddenly fall forward. You can imply from this that the bus's
velocity decreased
If the answer to you calculation has units of kg * m^2/s^2, what type of quantity could it be? (There could be more than one correct choice.)
work torque rotational kinetic energy
If the velocity of a car is non-zero, can the acceleration of the car be zero?
yes
Is it possible for an object moving with a constant speed to accelerate? Explain.
yes, although the speed is constant, the direction of the velocity can be changing
Is it possible for an object moving around a circular path to have both centripetal and tangential acceleration?
yes, this is possible if the speed is changing
A rocket moves through empty space in a straight line with constant speed. It is far from gravitational effect of any star or planet. Under these conditions, the force that must be applied to the rocket in order to sustain its motion is
zero