Physics Knowledge Questions

Three objects are located in the x-y plane as shown in the figure. Determine the x coordinate of the center of mass for this system of three objects A= 6.0kg, B= 2.0kg, C= 4.0 kg a) 5.6 b) 6.3 c) 7.6 d) 8.3 e) 8.9

6.3

Which one of the following statements is true concerning momentum? a) momentum is a force b) momentum is a velocity c) momentum is a scalar quantity d) the momentum of an object is always positive e) momentum is measured in kg * m/s

momentum is measured in kg * m/s

during a certain process, the linear momentum of a system is conserved, which one of the following statements concerning this system is correct? a) the vector sum of the momentum of the objects that make up the system is equal to zero kg * m/s b) the vector sum of any internal forces within the system results in an acceleration of one or more objects within the system c) the principle of the conservation of mechanical energy automatically applies to the system d) the vector sum of the average external forces acting on the system is equal to zero newtons e) no internal or external forces are acting on the objects within the system

the vector sum of the average external forces acting on the system is equal to zero newtons

Which one of the following statements concerning the center mass of an object is true? a) the velocity of the center of mass of a system of objects is constant when the sum of the external forces acting on the system is zero b) the center of mass of a system of objects cannot change even if there are forces acting on the objects c) all of an objects mass is located at its center of mass d) the velocity of the center of mass of a system of objects is greatly affected by a collision of objects within the system e) the center of mass of an object must be located within the object

the velocity of the center of mass of a system of objects is constant when the sum of the external forces acting on the system is zero

Two pucks on an air hockey table collide elastically. Complete the following statement: when such a collision occurs in two dimensions, the before and after velocities are best determined by a) using the fact that momentum is conserved and that the initial speeds of the objects must equal the final speeds of the objects b) remembering that momentum is a vector quantity that is conserved in each direction c) applying Newton's second law of motion and setting the net force equal to zero newtons d) making use of the work-energy theorem e) using the fact that the total energy is conserved

remembering that momentum is a vector quantity that is conserved in each direction

Which one of the following is not a unit of energy? a) joule, b) watt, c) newton * meter, d) kilowatt * hour, e) foot * pound

watt

work may be expressed using all of the following units except: a) watt, b) joule, c) N*m, d) erg, e) ft*lb

watt

A man carries a 12-kg chair up one flight of stairs to the second floor of his house. If the second floor is 3.3 m above the first floor, what is the change in the gravitational potential energy of the chair? a) -180 J b) +390 J c) +180 J d) -390 J e) +240 J

+390 J

Bird A, with a mass of 2.2 kg, is stationary while Bird B, with a mass of 1.7 kg, is moving due north from Bird A at 3 m/s. What is the velocity of the center of mass for this system of two birds? a) 1.4 m/s due north b) 0.77 m/s due north c) 1.7 m/s due north d) 0.77 m/s due south e) 1.4 m/s due south

1.4 m/s due north

Which one of the following expressions is equal to the kinetic energy of an object? a) mvt2 b) 1/2mv^2 c) Fd cos theta d) ma e) mgh

1/2mv^2

Alice and Bill, who happen to have the same mass, both want to climb to the top of a mountain. Bill wants the take the steep path straight up, but Alice wants to take the path that gently winds around the mountain even though it is 8x longer than the steep path. They both eventually reach the top of the mountain, but alice reaches the top in 1/3 the time that Bill takes using the steep route. How does the work that Alice did climbing the mountain compare with the amount that Bill did? a) Alice did 1/8 the amount of work that Bill did b) Alice did 1/3 the amount of work that Bill did c) Alice and Bill did the same amount of work d) Alice did twice the amount of work that Bill did e) Alice did three times the amount of work that Bill did

Alice and Bill did the same amount of work

Power may be expressed using the following units except: a) watt b) joules/second c) N * m * s d) erg/s e) ft * ib/h

N * m * s

Which on of the following situations is an example of a conservative force acting? a) a boat motor produces a propulsion force that moves the boat across a lake b) the tension force in the rope increased as the piano was lifted off the ground c) a child jumping on a trampoline is pushed upward by an elastic spring force d) a normal force pushes upward on a book as it sits on a table e) the static frictional force between the tires of a car and the road

a child jumping on a trampoline is pushed upward by an elastic spring force

In which one of the following situations will there be an increase in kinetic energy? a) a kicked football approaches its maximum height as it passes through the goal posts b) the planet venus moves in its nearly circular orbit around the sun c) a fan is switched from "low speed" to "high speed" d) a filing cabinet is pushed across a rough floor at constant speed e) a train is pulled up a mountain at a constant speed by a motor

a fan is switched from "low speed" to "high speed"

In which one of the following systems is there a decrease in gravitational potential energy? a) a large boulder rests at the bottom of a steep hill b) a helicopter takes off from the roof of a hospital and flies due west c) a child accidentally releases a helium-filled balloon and it flies upward into the cliuds d) a girl jumps down from a bed and lands on her feet e) a truck drives at an average velocity of 25 m/s, due north along a level, country road

a girl jumps down from a bed and lands on her feet

In which one of the following situations is zero net work done? a) a bunch of bananas are placed on a spring scale in the supermarket, b) a sky diver falls from an airplane before opening her parachute, c) a horse pulls a wagon at a constant velocity, d) a snowball rolls down a hill e) a skateboarder steps on a skateboard and begins to roll

a horse pulls a wagon at a constant velocity

In which one of the following situations is linear momentum not conserved? a) a golf ball is struck by a putter b) a bowling ball collides with ten pins c) a tree limb is struck by lightning and falls to the ground d) a bomb suspended by a string explodes into one hundred fragments e) an astronaut floating in space throws a hammer away and subsequently moves in the opposite direction

a tree limb is struck by lightning and falls to the ground

The momentum of an object is not dependent on which one of the following quantities? a) acceleration b) inertia c) mass d) speed e) velocity

acceleration

Complete the following statement: In an isolated system, the total mechanical energy remains constant if a) all exerted forces are conservative b) all exerted forces are non-conservative c) the work done by non-conservative forces is positive d) the work is done by non-conservative forces is negative e) an object returns to its starting position

all exerted forces are conservative

As the name implies, the impulse-momentum theorem provides a relationship between impulse and momentum. Which one of the following statements correctly describes that relationship? a) an impulse is equal to the work done on an object when a net force acts on an object and it has a displacement b) an impulse is equal to the change in an objects momentum that occurs when a net force acts on it c) an impulse is equal to one-half of the objects momentum squared d) and impulse is equal to the product of the net force acting on the object and its momentum e) and impulse is equal to the objects momentum divided by the product of the net force and the time interval during which the force acts

an impulse is equal to the change in an objects momentum that occurs when a net force acts on it

Which one of the following provides a basis to distinguish different types of collisions? a) conservation of linear momentum b) conservation of mechanical energy c) conservation of kinetic energy d) conservation of impulse e) conservation of mass

conservation of kinetic energy

Complete the following statement: The net work done by a conservative force acting on an object a) depends only on the time that the force is exerted b) depends only on the velocity of the object c) depends only on the starting and ending points d) is always equal to zero joules e) is always greater than zero joules

depends only on the starting and ending points

Complete the following statement: The change in momentum with respect to time for an object a) is always positive b) is always equal to zero c) has a constant value if the force acting on the object is conservative d) is equal in magnitude to the net force acting o the object, but opposite in direction e) is a scalar quantity that may be negative, zero, or positive

has a constant value if the force acting on the object is conservative

During a maneuver in space, a space craft separates into two pieces, each of mass m. Before the separation, the spacecraft was moving with a speed v. If one of the pieces is at rest after the separation, which one of the following statements concerning this maneuver is true? a) this maneuver conserves kinetic energy b) the maneuver does not conserve total energy c) this maneuver does not conserve momentum d) if one piece is at rest, the other is moving with a speed 2v e) one piece cannot be at rest. They must both be moving with a speed v/2

if one piece is at rest, the other is moving with a speed 2v

Which one of the following quantities is equal to the change in momentum of an object during a collision? a) impulse b) net force c) work d) change in kinetic energy e) maximum force

impulse

Complete the following statement: In situations involving non-conservative external forces, the work done by these forces a) is always negative b) is always equal to zero c) is always positive d) can either be positive or negative e) usually cannot be determined

is always negative

Momentum may be expressed using which of the following units? a) N/s b) kg/m c) kg * m/s d) kg/ (m * s) e) N * kg/s

kg * m/s

Which of the following units are used for an impulse? a) kg * m/s b) kg/m c) N/s d) kg/ (m * s) e) N * kg/s

kg * m/s

Which one of the following combinations of units is equal to joule? a) kg *m2/s, b) kg * m, c) kg * m/s, d) kg *m2/s2, e) kg * s

kg * m2/s2

Which one of the following quantities is conserved during an elastic collision, but not conserved during an inelastic collision? a) momentum b) kinetic energy c) total energy d) impulse e) net force

kinetic energy

a ball is thrown vertically upward in the air. Which one of the following quantities is necessarily equal to zero at the highest point of the ball's trajectory a) acceleration b)net force c) potential energy d) kinetic energy e) total mechanical energy

kinetic energy

Which one of the following choices is an example of a non-conservative force? a) elastic spring force b) gravitational force c) kinetic frictional force d) electrical force

kinetic frictional force

A boy of mass m runs with a speed v and jumps onto a sled on an icy pond. The sled was at rest before the boy jumped onto it. After the jump, the sled and a boy move at a speed v/2. What was the mass of the sled? a) m/2 b) m c) 2m d) 3m e) 4m

m

Which one of the following statements concerning the principle of the conservation of mechanical energy is true? a) mechanical energy is always conserved in situations where the kinetic energy is constant b) mechanical energy is always conserved in situations where the gravitational potential energy is constant c) mechanical energy is always conserved in situations where external non-conservative forces do not work d) mechanical energy is always conserved in situations where external conservative forces do not work e) mechanical energy is always conserved in situations where the gravitational potential energy is zero joules

mechanical energy is always conserved in situations where external non-conservative forces do not work

Which one of the following statements is true concerning momentum? a) momentum is a force b) momentum is a velocity c) momentum is a scalar quantity d) the momentum of an object is always positive e) momentum and impulse are measured in the same units

momentum and impulse are measured in the same units

A rifle of mass M is initially at rest. A bullet of mass m is fired from the rifle with a velocity v relative to the ground. Which one of the following expressions gives the velocity of the rifle relative to the ground after the bullet is fired a) -mv b) mv c) Mv/m d) mv/ M e) -mv/ M

mv/ M

Sarah carries a heavy box of books down a flight of stairs from the third floor to the first floor. Which one of the following statements best describes the work done on the box by Sarah? a) sarah doesn't do any work on the heavy box of books b) sarah does a small amount of negative work on the heavy box of books c) sarah does a small amount of positive work on the heavy box of books d) sarah does a large amount of negative work on the heavy box of books e) sarah does a large amount of positive work on the heavy box of books

sarah does a large amount on negative work on the heavy box of books

In which of the following circumstances does the force do positive work on the object? a) the direction of the force is perpendicular to the object's displacement, b) the direction of the force is the opposite direction to the object's placement, c) no matter the direction of the force, positive work will be done if there is a displacement of the object, d) the direction of the force is in the same direction as the objects displacement, e) the object's displacement is zero meters as the force is applied

the displacement of the force is in the same direction as the objects displacement

Complete the following statement: the center of mass of a system of particles has a constant velocity if a) the velocity of the center of mass is initially zero b) the particles are distributed symmetrically around the center of mass c) the forces exerted by the particles on each other sum to zero d) the center of mass is at the geometric center of the system e) the external forces acting on particles of the system sum to zero

the external forces acting on particles of the system sum to zero

What is the relationship between the gravitational potential energy of an object and the work done on the object by the gravitational force? a) the work is equal to the gravitational potential energy b) the negative of the work is equal to the change in the gravitational potential energy c) the negative of the work is equal to the square of the gravitational potential energy d) the work is equal to the square of the gravitational potential energy e) the work is equal to one-half of the gravitational potential energy

the negative of the work is equal to the change in the gravitational potential energy

Which one of the following is an example of an object with a non-zero kinetic energy? a) a train is parked in a train station b) a car rests at the top of a hill c) the pendulum of a grandfather clock is still d) a boulder rests at the bottom of a cliff e) the international space station orbits the earth

the international space station orbits the earth

Which one of the following statements concerning kinetic energy is true? a) the kinetic energy of an object is directly proportional to its speed b) the kinetic energy of an object is expressed in watts c) the kinetic energy of an object is a quantitative measure of its inertia d) the kinetic energy of an object always has a positive value e) the kinetic energy of an object is always equal to the object's potential energy

the kinetic energy of an object always has a positive value

two objects are involved in an elastic collision. Which one of the following statements concerning this situation is false? a) the total momentum is conserved b) the magnitude of the force exerted by each object on the other object is equal c) the kinetic energy of each object is the same before and after the collision d) the total kinetic energy before the collision is equal to the total kinetic energy after the collision e) the total kinetic energy is conserved

the kinetic energy of each object is the same before and after the collision

An arrow is launched straight up from the surface of the Earth, which one of the following statements describes the energy transformation of the arrow as it rises? Neglect air resistance. a) the kinetic energy of the arrow increases and its potential energy decreases b) both the potential energy of the arrow and its total energy increase c) the kinetic energy of the arrow decreases as the potential energy increases d) both the kinetic energy of the arrow and its potential energy remain constant e) the total energy of the arrow increases

the kinetic energy of the arrow decreases as the potential energy increases

the power due to a force depends on which of the following parameters? a) the magnitude of the force and the displacement of the object b) the magnitude of the force and the velocity of the object c) the mass of the object and the velocity of the object d) the work done on the object and its displacement e) the mass of the object and the displacement of the object

the magnitude of the force and the velocity of the object

Which one of the following statements concerning the momentum of a system when the net force acting on the system is equal to zero newtons is true? a) the momentum of the system is increasing b) the momentum of the system is decreasing c) the momentum of the system is equal to zero kg * m/s d) the momentum of the system has a constant value e) the momentum of the system has a negative value

the momentum of the system has a constant value

which one of the following statements concerning the momentum of a system when the net force acting on the system has a positive value is true a) the momentum of the system is increasing b) the momentum of the system is decreasing c) the momentum of the system is equal to zero kg * m/s d) the momentum of the system has a constant value e) the momentum of the system has a negative value

the momentum of the system is increasing

Which on of the following statements concerning the principle of conservation of energy is false? a) the total energy in the universe has a constant value b) kinetic energy may be converted into gravitational potential energy and heat c) thermal energy my be converted into kinetic energy and kinetic energy may be converted into thermal energy d) chemical energy may be converted into thermal energy and gravitational potential energy e) the net work done on an object must be zero joules since energy is neither created nor destroyed in the process

the net work done on an object must be zero joules since energy is neither created nor destroyed in the process

A ball is constrained to follow a circular path by a conservative force. During a time interval t, the ball makes exactly one revolution. Which one of the following statements concerning the net work is done on the ball during time t is true? a) the net work depends only on the time t b) the net work depends only on the velocity of the ball c) the net work depends only on the radius of the circle d) the net work is equal to zero joules e) the net work is greater than zero joules

the net work is equal to zero joules

Complete the following statement: the center of mass is a) the region of an object where the density has the largest value b) the region of an object where most of the mass is located c) the point within an object that moves as if all the object's mass were located there d) the point at the geometrical center of an object e) the only point on an object at which the gravitational force acts

the point within an object that move as if all the object's mass were located there

A rocket propelled forward as very high speed gases are ejected out of its back, which one of the following is the best explanation as to why the rocket is propelled forward? a) the rocket is propelled forward due to the conservation of energy b) the rocket is propelled forward due to the conservation of momentum c) because the gases are pushing against the air, the air propels the rocket forward d) the rocket is propelled forward because both energy and momentum must be conserved e) the high speed gases push on the rocket as they are ejected and propel it forward

the rocket is propelled forward due to the conservation of momentum

A collision between two objects is inelastic. Which one of the following statements concerning this situation is true? a) the vector sum of the velocities of the two objects is equal to zero m/s after the collision b) the total momentum of the objects after the collision is less than it was before the collision c) the objects bounce away from each other after the collision d) the kinetic energy of the objects is zero joules after the collision e) the total kinetic energy of the objects after the collision is less than it was before the collision

the total kinetic energy of the objects after the collision is less than it was before the collision

a collision between two objects is elastic. Which one of the following statements concerning this situation is true? a) the total kinetic energy of the objects is the same before and after the collision b) the total momentum of the objects is zero kg*m/s after the collision c) the objects stick together and move as one object after the collision d) the kinetic energy of the objects is zero joules after the collision e) the vector sum of the velocities of the two objects is equal to zero m/s after the collision

the total kinetic energy of the objects is the same before and after the collision

Complete the following statement: If positive work is done on a moving object, a) the velocity of the object will increase b) the velocity of the object will decrease c)the kinetic energy of the object will decrease d) the velocity of the object will not change e) the direction of the acceleration of the object will be opposite to its displacement

the velocity of the object will increase

Complete the following statement: A force that acts on an object is said to be conservative if: a) the work it does on the object is equal to the increase in the object's kinetic energy b) the work it des on the object is independent of the path of the motion c) it always acts in the direction of the motion of the object d) it results in a change in the object's kinetic energy e) it obeys Newton's laws of motion

the work it does on the object is independent of the path of the motion

Complete the following statement: The total mechanical energy of a system remains unchanged if a) the external forces acting on the system are non conservative b) the external forces acting on the system are conservative c) the kinetic energy is constant d) the potential energy is constant e) there are no external forces acting on the system

there are no external forces acting on the system

A n object is initially at height y1. After a time interval t, the object is located at height y2. The work done by the gravitational force on the object is dependent on which of the following quantities? a) y1 - y2 b) the path taken from y1 to y2 c) the time interval t taken to move from y1 to y2 d) choices a and b e) choices a and c

y1 - y2

A 5.0-kg ball on the end of a chain is whirled at a constant speed of 1.0 m/s in a horizontal circle of radius 3.0m. What is the work done by the centripetal force during one revolution? a) 2.5 J, b) 1.7 J, c)1.2 J, d)0.56 J e) zero J

zero J