Final Exam Multiple Choice
Which property of an object is likely to change on another planet?
Weight
An object is thrown straight up. What is the work done by the gravitational force while the object moves up and then down?
Work is negative on the way up, work is positive on the way down
A boy rides a bike at a constant velocity. What is the net force?
Zero
A construction worker holds a heavy tool box. How much work is done by the worker?
Zero
A container with a mass m of __kg is lifted to a height of __m and then returned back to ground level. How much work is done by the gravitational force?
Zero
A spacecraft moves around the Earth in a circular orbit with a constant radius. How much work is done by the gravitational force on the spacecraft during on revolution?
Zero
A truck driver is trying to push a loaded truck with an applied force. Unfortunately, his attempt was unsuccessful the truck stays stationary no matter how hard the driver pushes. How much work is done by the driver?
Zero
A box is being pushed by a constant force along a horizontal surface. If the object's velocity is constant, we can infer that there is _________ acting on the box
a frictional force
The acceleration of an object is proportional to
a net force acting on it
The acceleration of an object is inversely proportional to
its mass
An object moves at a constant speed of 6m/s. This means that the object:
Moves 6 meters every second
When a baseball is struck by a bat, the force of the bat on the ball is equal and opposite to the force of the ball on the bat. This is an example of
Newton's third law
A spacecraft travels at a constant velocity in empty space far away from any center of gravity. What force is applied on the spacecraft?
No applied force is required to maintain a constant velocity
You are standing in a moving bus, facing forward, and you suddenly move forward as the bus comes to an immediate stop. What force caused you to move forward?
Normal force due to your contact with the floor of the bus
Newton's third law refers to "action-reaction forces". These forces always
Occur in pairs and never act on the same object
A spacecraft starts on earth is moving to Mars. What is true about the gravitational force on the spacecraft due to earths attraction?
The spacecraft is never beyond earths gravitational attraction
A student is doing a hand-stand. A reaction pair of forces is best described as
The student pushes down on the ground; the ground pushes up on the student
A ball is thrown straight up. At the top, the magnitude of the net force acting on it is
equal to mg
A planet has a mess of two times that of earth and a radius of twice that of earth? What is the acceleration due to gravity on the planet in terms of the acceleration on earth?
g/2
If a book on the dashboard of your car suddenly flies toward you, the forward velocity of the car must have
increased
An object falls downward, KE always...
increases
What happens to the gravitational field if the distance from the center of an object doubles?
it is cut to 1/4
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
A system is:
the part of the universe that contains the objects we are interested in
The environment is defined as:
the part of the universe that does not contain the objects we are interested in
The acceleration due to gravity is higher on Jupiter than on Earth. The mass and weight of a rock on Jupiter compared to that on Earth would be
the same and more
A closed system is:
unaffected by external forces
You are standing in a moving bus, facing forward, and you suddenly fall forward. You can infer from this that the bus's
velocity decreased
A ball is thrown straight up from point A, reaches a maximum height at point B, and then falls back to point C. What is true about the direction the ball's velocity and acceleration between point A and B?
v⬆️ a⬇️
A ball is thrown straight up from point A, reaches a maximum height at point B, and then falls back to point C. What is true about the direction the ball's velocity and acceleration between point B and C?
v⬇️ a⬇️
As you are sitting in a chair, you feel the chair pushing up on you. The reaction force in this situation is
you pushing down on the chair
A block of mass m is moved over a distance d. An applied force F is directed perpendicularly to the block's displacement. How much work is done on the block by the force F? (Force up, displacement right)
zero
A rocket moves through empty space in a straight line with constant speed. It is far from the 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
In order for a rocket ship in deep space, far away from any other objects, to move in a straight line with a constant velocity it must exert a net force that is
zero
When you sit on a chair, the net external force on you is
zero
Why is it so much more difficult to get a heavy table to start moving, than it is to keep it moving?
μs > μk (static > kinetic)
A race car moving west beings to slow down after crossing a finish line. What is the correct direction of the car's acceleration?
➡️
A truck travels east with an increasing velocity. What is the correct direction of the car's acceleration?
➡️
A motorbike travels east and beings to slow down before a traffic light. What is the correct direction of the motorbike's acceleration?
⬅️
Action-reaction forces are
equal in magnitude but point in opposite directions
A block of mass m is moved over a distance d. An applied force F is opposite to the block's displacement. How much work is done on the block by the force F? (Force left, displacement right)
-Fd
An applied force F accelerates an object from rest to a velocity v. How much work is done by the applied force F?
1/2mv^2
In the diagram shown above, two blocks A and B with masses m and 2m are in contact on a horizontal frictionless surface. A force F is applied to block A. What is the force exerted by block A on block B?
2F/3 [F=ma, F=2m(F/3m), 2F/3] (2\3 mass of system)
An elevator of mass M is pulled upward by a cable; the elevator has a positive, but decreasing, velocity. What is the tension in the cable?
Between zero and Mg
In the diagram shown above, two blocks A and B with masses m and 2m are in contact on a horizontal frictionless surface. A force F is applied to block A. What is the acceleration of the system two blocks?
F/3m [F=ma, F=3m(a) /3m, a=F/3m]
A block of mass m is pulled over a distance d by an applied force F which is directed in parallel to the displacement. How much work is done on the block by the force F? (Force right, displacement right)
Fd
A truck driver slams on the brakes of a moving truck with a constant velocity v, as a result of his action the truck stops after traveling a distance d. If the driver had been traveling with twice the velocity, what would be the stopping distance compared to the distance in the first trial?
Four time greater
A car and a delivery truck both start from resort and accelerate at the same rate. However, the car accelerates for twice the amount of time as the truck. What is the distance of the car compared to the truck?
Four times as much
An archer is practicing with an arrow bow shoots an arrow straight up two times. The first time the initial speed is v0 and the second time he increases the initial speed to 4v0. How would you compare the maximum height in the second trial to that in the first trial?
Four times greater
An elevator of mass M is pulled upward by a cable; the elevator has a positive, increasing, velocity. What is the tension in the cable?
Greater than Mg
the discovery of universal gravitation is associated with
Isaac Newton
what happens to the gravitational field if the mass of a planet doubles?
It doubles
A cannon fires a cannonball and recoils backward. What is true about the momentum of the system?
It happens because the momentum of the system is conserved
What happens to the total energy of a moving object if all the applied forces are conserved?
It remains constant
An object is released from rest and falls in the absence of air resistance. What is true about its motion?
It's acceleration is constant
A ball is thrown straight up from point A, reaches a maximum height at point B, and then falls back to point C. What is true about the direction the ball's velocity and acceleration the highest point B?
It's velocity is zero and acceleration is down and non-zero constant
Which force is directly responsible for your ability to walk, and to stop?
Kinetic friction
The acceleration due to gravity is lower on the Moon than on Earth. What about the mass and weight of an astronaut on the Moon's surface, compared to Earth?
Mass is the same, weight is less
A container of __kg is lifted to a height of __m. How much work is done by the gravitational force? (How do you solve it?)
Solve by mgh (NEGATIVE)
A container of __kg is lifted to a height of __m. How much work is done by the external force? (How to you solve it)
Solve by mgh (POSITIVE)
A passenger standing in a moving bus, facing forward suddenly falls backward. What did the bus do?
Speed up
A rocket moves away from the surface of earth. As the distance are from the center of the planet increases, what happens to the force of gravity on the rocket?
The force decreases inversely proportional to (1/r^2)
A car traveling at 40m/s strikes a mosquito. What is true about the force?
The force on the mosquito is equal to the force on the car. Mass causes the damage.
A loaded truck collides with a car causing huge damage to the car. What is true about the collision?
The force on the truck is the same in magnitude as the force on the car
An apple hangs on a tree on earth. What is true about the forces?
The forces on the apple and Earth are equal
What happens to the kinetic energy of a moving object if the net work done is positive?
The kinetic energy increases
An object of mass m sits on a flat table. The Earth pulls on this object with force mg, which force is the action force. What is the reaction force?
The object pulling upward on the Earth with force mg
An object moves with a constant acceleration of 5m/s^2. That means the object:
The object's velocity increases by 5m/s each second
Earth pulls downward on a pen, of mass m, which is sitting on a table; the magnitude of the force is mg. If that is called the action force, what is the reaction force?
The pen pulling upward on Earth with a force equal to mg
Earth pulls downward on a pen, of mass m, which sitting on a table; the magnitude of the force is MG. If that is called the action force, what is the reaction force?
The pen pulling upward on Earth with a force equal to mg
What happens to the gravitational potential energy of a moving object of the work done by the gravitational force is negative?
The potential energy increases
A package is dropped from an air balloon two times. In the first trial distance between the balloon and the surface is H and in the second trial 4H. Compare the time it takes for the package to reach the surface in the second trial to that in the first trial?
The time in the second trial is four times greater
A traffic light is suspended from a cable. Earth pulls downward on the traffic light with a force of 1500N. If this is the "action force," what is the "reaction force"?
The traffic light pulling upward on Earth with a 1500N force
A football, hockey puck and tennis ball all fall down in the absence of air resistance. What is true about their acceleration?
They all fall down with the same constant acceleration
A tennis ball is dropped from the top of a tall building. A second tennis ball is thrown down from the same building. What is true about the acceleration of each tennis ball.
They both fall with the same acceleration because they are in free fall
Two baseballs are thrown from the roof of a house with the same initial speed, one is thrown up, and the other down. Compare the speeds of the baseballs just before they hit the ground
They both move with the same speed
Which of Newton's laws best explains why motorists should wear seat belts?
Third law
A car and a delivery truck both start from resort and accelerate at the same rate. However, the car accelerates for twice the amount of time as the truck. What is the final speed of the car compared to the truck?
Twice as much
A modern car can develop an acceleration four times greater than an antique car. If they accelerate over the same distance, what would be the velocity of the modern car compared to the antique car?
Twice as much
Name a vector quantity
Velocity and displacement
A net force F accelerates a mass m with an acceleration a. If the same net force is applied to mass 5m then the acceleration will be
a/5
An open system:
allows objects to enter and is affected by external forces
If you exert a force F on an object which has a much greater mass than you do, the force which the objects exerts on you will
be of magnitude F and in the opposite direction
Two objects with equal masses of 1 KG each are separated by a distance of 1M. The gravitational force between objects is
equal to g
An object falls downward, GPE always...
decreases
If the speed of a car is halved, the KE of the car is:
doubled
In the absence of an external force, a moving object will
move with a constant velocity
When the rocket engines on a spacecraft are suddenly turned off while traveling off while traveling in empty space, the spacecraft will
move with a constant velocity
If the speed of a car is doubled, the KE of the car is:
quadrupled