Physics Final 2021
Work is a _____ quantity; it is fully described by stating its _____
scalar, magnitude alone
Consider the three situations described below. In which situation(s) would the mechanical energy NOT be conserved?
-A car skids to a stop across a level highway -A mountain climber slowly but steadily ascends a steep cliff
Which of the following are examples of work being done (either positive or negative) upon an object
-A rightward Force is applied to an object to move it to the right at a constant speed -A rightward force is applied to an object to accelerate it to the right -An upward force is applied to a downward moving object to slow it down as it moves -An upward force is applied to an object to move upward at a constant speed -An upward force is applied to an object to accelerate it upward
Some forces are categorized as conservative forces (or internal forces) while others are categorized as non-conservative forces (or external forces). Which of the following forces are generally categorized as non-conservative (or external) forces?
-Air Resistance Force -Tension Force -Applied Force -Force of Friction -Normal Force
Some forces are categorized as conservative forces (or internal forces) while others are categorized as non-conservative forces (or external forces). Which of the following forces are generally categorized as conservative (or internal) forces?
-Force of Gravity -Spring Force
A 5-Newton friction force acts upon a 2-kg object to slow it down as it moves across a horizontal surface over a distance of 4 meters. Which of the following forces are doing work up on the object (either positive or negative) [in the diagram shown, all forces are drawn equally]
-Friction
A 5-Newton Force is applied to a 2-kg object to move it across a horizontal surface at a constant speed for a distance of 4 meters. Which of the following forces are doing work upon the object (either positive or negative) [in the diagram shown, all forces are drawn equally]
-Friction -Applied
Which of the following variations will increase the potential energy of an object
-Increase the object's mass -Increase the object's height
Which of the following variations will increase the kinetic energy of an object
-Increase the object's speed -Increase the object's mass
An object will definitely have potential energy if it is ______
-Moving above the ground (a non-zero height) -At rest above the ground (a non-zero height)
An object will have kinetic energy if it is _____
-Moving above the ground (a non-zero height) -Moving on the ground (height = 0 meters) -Moving
The kinetic energy (KE) and potential energy (PE) values are shown for various locations. In this example, _____
-Total mechanical energy is conserved
10-kg object is moving to the right at a constant velocity of 4 m/s. Which one of the following horizontal forces is required to maintain this state of motion
0 Newton's
Which of the following would have the effect of decreasing the acceleration of an object? Select all that apply.
1. Decreasing the net force experienced by the object. 2. Tripling the mass of the object
Which of the following statements are TRUE? Select all that apply (Newton's Second Law
1. The mass of an object on the moon will be the same as its mass on Earth 2. On Earth, more massive objects weigh more than less massive ones
Which of the following descriptions COULD be true of an object that is at equilibrium? Select all that apply
1. The object is moving 2. The object is at rest 3. The object is moving with constant velocity
Which of the following would have the effect of decreasing the acceleration of an object? Select all that apply
1. Tripling the mass of an object 2. Decreasing the net force experienced by the object
When all individual forces acting upon an object are balanced, it is the natural tendency of the object to _____
1. keep their velocity constant (either at zero or non-zero) 2. Maintain their state of motion
An object has a kinetic energy of 18 J. If the object's speed is tripled, then its new kinetic energy will be _____ Joules
162 Joules
A 75-kg mountain climber ascends (climbs) 20 meters up a steep cliff in 60 seconds. The power rating of the mountain climber is _____ Watts
250 Watts
Ball A and ball B travel at the same speed; however, ball A has triple the mass of ball B. What is the ratio of the kinetic energy of ball A to ball B.
3:1
The kinetic energy and the potential energy of a roller coaster car at various locations are shown. The total mechanical energy of the car at position D is _____ Joules [position D: KE= 250,000 PE= 150,000]
400,000 Joules (add KE and PE)
A horizontal force of 120 Newton is applied to a 15-kg crate to move it horizontally a distance of 6 meters across a concrete floor at a constant speed of 4 m/s. The task requires 1.5 seconds. The power rating for the person applying the force is approximately ______ Watts
480 Watts
An object has a kinetic energy of 61 J. If the object's speed increases by a factor of 3, then its new kinetic energy will be ____ Joules
549 Joules
Jack and Jill are doing a physics lab. They apply a 30-Newton force to a 6-kg cart to pull it up an inclined plane at a constant speed. The plane is inclined at a 30-degree angle. Jack and Jill are exerting a force on the cart that is parallel to the inclined plane in order to displace it 2.0 meters along the incline to a final height of 1 meter. During this lab, the amount of work done on the cart is approximately _____ Joules.
60 Joules
In a physics lab, a 60-kg student runs up a 2.0-meter tall flight of stairs in 1.5 seconds. The student's power rating is approximately ______ Watts
800 Watts
In which of the following scenarios is work done
A car decelerates while traveling on a flat stretch of road.
Two identical airplanes are flying over Omaha. airplane A is flying at twice the speed and twice the altitude (height above the ground) as airplane B. Compared to airplane B, what is the potential energy of airplane A?
A has twice the potential energy
The essential difference between work and power is that power is ______
A rate quantity and work is not a rate quantity
In which of the following cases is no work done
A weightlifter holds a barbell overhead
In an amusement park ride, a 400-kg suspended car starts from rest at ground level (A) and is accelerated across a level section of track and then ascends a steep hill to a peak height of 40 meters (B) before coasting back towards its original position. Use g = 10 m/s/s to perform an energy analysis and fill in all the blanks
A- KE: 0 A- PE: 0 Between A and B- W: 160,000 B- KE: 0 B- PE: 160,000
An 800-kg car moving with a speed of 28 m/s (at A) puts on the brakes and slows down to a speed of 14 m/s (at B). Use g = 10 m/s/s to perform an energy analysis and fill in all the blanks.
A- KE: 313,600 A- PE: 0 Between A and B- W: -235,200 B- KE: 78,400 B- PE: 0
A rightward-moving truck skids to a stop from a very high speed with its wheels locked it has_____
Air resistance, friction, normal, gravitational forces
Define Newton's 1st Law of motion
An object in motion will stay in motion and an object at rest will stay at rest unless an unbalanced force acts on it (in the same speed and direction)
The path of a projectile moving through the air is shown in the diagram below. Frictional forces can be assumed to be negligible. Perform an energy analysis and answer the questions corresponding to the blanks in the diagram [A- KE: 22 PE: 0] [B- KE: _____ PE: 7] [C- KE: _____ PE: 18] [D- KE: 9 PE: _____] [E- KE: _____ PE: _____]
B- KE: 15 C- KE: 4 D- PE: 13 E- KE: 22 E- PE: 0
The path of a sledder gliding across the ice and snow is shown in the diagram below. Frictional forces can be assumed to be negligible. Perform an energy analysis and fill in all the blanks [A- KE: 2,000 PE: 10,000] [B- KE: _____ PE: 6,000] [C- KE: _____ PE: 0] [D- KE: 9,000 PE: _____] [E- KE: _____ PE: _____]
B- KE: 6,000 C- KE: 12,000 D- PE: 3,000 E- KE: 12,000 E- PE: 0
An object that is at equilibrium is an object upon which all the forces are ____
Balanced
A dad gives his child on a sled a long push to set him in motion along the level surface. This situation can best be described as a transformation of _____
Chemical energy into Kinetic energy
A hockey stick hits a puck on the ice. Identify an action-reaction pair in this situation.
The stick exerts a force on the puck; the puck exerts a force on the stick.
A box is being accelerated across a rough, level surface. A force is being applied to the box in an upward and a rightward direction (as shown below). This force makes an angle of 30 degrees with the horizontal. If the angle at which the force is exerted is increased to 45 degrees, then the friction force would ____.
Decrease
Suppose that an object moves downward with a decreasing speed. In this situation, the object's kinetic energy would _____, its potential energy would _____, and its total mechanical energy would _____
Decrease Decrease Decrease
Suppose that an object slows down while moving horizontally. In this situation, the object's kinetic energy would _____, its potential energy would _____, and its total mechanical energy would _____
Decrease Remains the same Decrease
An object is placed upon an inclined plane with an incline angle of 25 degrees. As the incline angle is INCREASED towards 90 degrees, the normal force experienced by the object ____
Decreases
If the net work done on an object is negative, then the object's kinetic energy
Decreases
A leftward moving object is coasting to a stop along a straight, level surface. The net force acting upon the object MUST be ____
Directed rightward
If an object has potential energy, then its kinetic energy is 0 Joules
False
Inertia is a force that keeps stationary objects at rest and moving objects in motion at a constant velocity
False
Which of the following is the cause of an acceleration?
Force
Suppose that an object moves upward with an increasing speed. In this situation, the object's kinetic energy would _____, its potential energy would _____, and its total mechanical energy would _____
Increase Increase Increase
Suppose that an object speeds up while moving horizontally. In this situation, the object's kinetic energy would _____, its potential energy would _____, and its total mechanical energy would _____
Increase Remain the same Increase
A baseball player moving with a speed of 8.5 m/s (initial state) dives head-first and slides to a stop (final state) along level ground (choose the appropriate energy bar)
Initial: 4 Kinetic -4 Work Final: None
You slam on the brakes of your car in a panic, and skid a certain distance on a straight, level road. If you had been traveling three times as fast, what distance would the car have skidded, under the same conditions?
It would have skidded nine times farther
The standard metric unit of work is the _____
Joule
A box is being accelerated across a level surface. A force is being applied to the box in an upward and rightward direction (as shown below). In this situation, the normal force is ____ the force of gravity
Less than
Mac and Tosh run up the same hill. Mac has twice the mass as Tosh. Tosh climbs up the hill in one-half the time as Mac. In this situation, ______
Mac does more work than Tosh, but they have the same power rating
A softball player is sliding into third base. Once she hits the dirt, the force of friction acts upon her to slow her down as she slides a distance of 1.5 m across the distance. In this example, friction is doing _____ work upon the player
Negative
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
A joule is equivalent to a
Newtons x Meters
In order for an object to conserve its total mechanical energy it is absolutely necessary that _____
Non-conservative (i.e., external) forces do NOT do net work upon the object
Two objects of identical mass begin from rest at the same height at the top of two different hills - hill A and hill B. The hills are inclined at two different angles (see diagram). The objects are released from rest and slide to the bottom; resistance forces can be considered to be negligible. The object on top of hill _____ will have the greatest speed at the bottom of the incline [the diagram shows that hill A is less steep than hill B]
Nonsense! Both objects will have identical speeds at the bottom.
A person is standing upon the ground has_____
Normal and Gravitational Forces
If the only forces doing work upon an object are conservative (or internal) forces, then the total mechanical energy of the object will _____ If the only forces doing work upon an object are non-conservative (or external) forces, then the total mechanical energy of the object will _____
Not change Change (either increase or decrease)
A child is pushing an empty box across the living room floor. The child exerts a constant rightward force upon the box to move at a distance of 2 meters to the right. In this example, the child is doing _____ work upon the box
Positive
Suppose that an object moves upward at a constant speed. In this situation, the object's kinetic energy would _____, its potential energy would _____, and its total mechanical energy would _____
Remain the same Increase Increase
Suppose that an object moves downward at a constant speed. In this situation, the object's kinetic energy would _____, its potential energy would _____, and its total mechanical energy would _____
Remain the same Decrease Decrease
If you push twice as hard against a stationary brick wall, the amount of work you do
Remains constant at zero
Consider the work energy bar charts shown below. Select any bar chart that portrays a situation in which mechanical energy is NOT conserved
Select each bar chart that includes work (either positive or negative)
An elevator is suspended by cables and slowly descends through the elevator shaft. There is no contact with the walls of the elevator shaft. Neglect air resistance. The elevator has_____
Tension and Gravitational Forces
The total mechanical energy of an object is ______
The sum of its kinetic energy and its potential energy
Define Newton's Second Law
The acceleration of an object is proportional to the resultant force acting on the object, and inversely proportional to the mass of the object.
If the sign of work is negative
The displacement is in the direction opposite the force
Power is defined as ______
The rate at which work is done upon an object
Student A and student B are doing two identical tasks involving physical work. Student A does the task in more time than student B. In this physical situation, _____
The two students do the same amount of work but student B has the greater power rating
A lightweight object and a very heavy object are sliding with equal speeds along a level frictionless surface. They both slide up the same frictionless hill. Which rises to a greater height?
They both slide to the same height.
The law of inertia (Newton's first law) applies _____
To both moving and non moving objects
Mac and Tosh are arguing in the cafeteria. Mac says that if he flings the jello with a greater speed it will have a greater inertia. Tosh argues that inertia does NOT depend upon speed, but rather upon mass. Who is correct?
Tosh
Which of the following is a true statement about the conservation of energy?
Total energy is always conserved
Which of the following refers to the sum of kinetic energy and all forms of potential energy
Total mechanical energy
If non-conservative forces (i.e., external forces) are acting upon an object, then the total mechanical energy of that object could still remain constant
True
The standard metric unit of power is a ______
Watt
The force of gravity that acts upon an object is referred to as the _____ of the object.
Weight
A bucket full of water is slowly lifted by a rope out of a deep well. In this situation, the total mechanical energy of the bucket of water _____
Will definitely change
A car is skidding to a stop. In this situation, the total mechanical energy of the car _____
Will definitely change
A parachutist is falling downward, encountering a large amount of air resistance. In this situation, the total mechanical energy of the parachutist _____
Will definitely change
If both conservative (i.e., internal) and non-conservative (i.e., external) forces are doing net work upon an object, then the total mechanical energy of the object _____
Will definitely change
A dart is traveling through the air towards a dart board. Assume that air resistance is negligible. In this situation, the total mechanical energy of the dart _____
Will remain constant
A roller coaster car is coasting down the first drop of the track. Assume that resistance forces have no effect on the car's motion. In this situation, the total mechanical energy of the car _____
Will remain constant
A man is walking through an airport with a suitcase. The man exerts a constant upward force upon the suitcase as he walks a distance of 20 meters. In this example, the man is doing _____ work upon the suitcase
Zero
A packing crate slides down an inclined ramp at constant velocity. Thus we can deduce that
a frictional force is acting on it
Gravitational potential energy is always measured in relation to
a zero or reference level
Suppose that an astronaut throws a rock in outer space at a location far from significant influences of gravity and air resistance. One would expect that the rock would ____.
continue in motion with the same speed and direction
In order to have work done upon an object, there must be a _____ to cause a _____
force acting upon the object, displacement
A free-body diagram represents all of the following except
forces exerted by the object.
The amount of matter or "stuff" in an object is referred to as the _____ of the object
mass
It's more difficult to start moving a heavy carton from rest than it is to keep pushing it with constant velocity, because
mk < ms (m=u)
Kinetic energy is the energy that an object possesses due to its _____ potential energy is the energy that an object possesses due to its _____
motion, position
What are the units of the coefficient of friction?
no units
The force that keeps you from sliding on an icy sidewalk is
static friction
A vector component describes _____
the effect of a vector in a given direction
If you were in a spaceship and fired a cannonball into frictionless space, the amount of force needed to keep the cannonball in motion would be ____
zero, since no force is necessary to keep an object moving