physics final

if the mass of the earth and all objects on it were suddenly doubled, but size remained the same, the acceleration due to gravity at the surface would become

2 times what it is now

a 5kg ball collides head-on with a 10kg ball, which is initially stationary. the collision is inelastic. which is true?

the magnitude of the change of velocity of the 5kg ball experiences is greater than that of the 10kg ball.

an object is moving with a constant velocity. which statement is true?

the net force on the object is zero

When you ride a bicycle, in what direction is the angular velocity of the wheels?

to your left

a refrigerator increase the entropy of its hot reservoir at the same time as it decreases the entropy of its cold reservoir

true

if 2 different gases are at the same temperature, the average translational kinetic energy per molecule must be the same for both of them.

true

if an object remains at rest, then the sum of both the external torques and the external forces on the object must be zero

true

if the graph of the position as a function of the time for an object is a horizontal line, that object cannot be accelerating

true

the magnitude of a vector cannot be smaller than the magnitude of any of its components

true

a bow slides down a frictionless plane inclined at an angle theta above the horizontal. the gravitational force on the box is directed

vertically

a spring stretches by 21cm when a 135 N object is attached. what is the weight of a fish that would stretch the spring by 31cm?

199N

a 95M force exerted at the end of a 0.5m long torque wrench gives rise to a torque of 15Nm. what is the angle (assumed to be less than 90) between the wrench handle and the direction of the applied force?

18 degrees

a sealed 89m^3 tank is filled with 6000 moles of oxygen gas at an initial temperature of 270K. the gas is heated to a final temperature of 350K. the atomic mass of oxygen is 16g/mol, and the ideal gas constant is R=8.314 J/molK. the initial pressure of the gas is closest to

0.15 MPa

What is 0.674 / 0.74 to the proper number of significant figures?

0.91

a students slides her 80 kg desk across the level floor of her dormitory room a distance 4m at constant speed. if the coefficient of kinetic friction between the desk and the floor is 0.400, how much work did she do?

1.26 kJ

the figure shows 2 forces acting on an object. they have magnitudes f1=9.6N and f2=3.2N. what third force will cause the object to be in equilibrium?

10N at 162 degrees counterclockwise from F1

During each cycle of its operation, a refrigerator absorbs 230 J of heat from the freezer and expels 356 J of heat to the room. how much work input is required in each cycle?

126 J

a hot air balloon has a volume of 2.00x10^3 m^3 when fully inflated, and the air inside the balloon is always at atmospheric pressure of 1.01x10^5 because of the large opening used to fill the balloon and heat the air inside it. what is the mass of hot air inside the balloon if its temperature is 120 degrees celsius?

1780 kg

a rock is thrown at a window that is located 18m above the ground. the rock is thrown at an angle of 40 degrees above horizontal. the rock is thrown from a height of 2m above the ground with a speed of 30 m/s and experiences no appreciable air resistance. if the rock strikes the window on its upward trajectory, from what horizontal distance from the window was it released?

27.3m

vectors A and B are shown in the figure. vector c is c=b-a. the magnitude of vector a is 16.0 units and the magnitude of vector b is 7.00 units. what is the angle of vector c, measured counterclockwise from the +x axis?

287 degrees

the temperature in your classroom is closest to

295K

a firecracker breaks up into several pieces, one of which has a mass of 200g and flies off along the y-axis with a speed of 45 m/s. what are the magnitude and direction of the total momentum of these two pieces?

361 kgm/s at 0.983 degrees from the x-axis

the number 0.003010 has

4 significant figures

an object has a position given by r=[2m+2m/st] + [3m- 1m/s^2] where quantities are in SI units. what is the speed of the object at time t=2s?

4.47 m/s

2 planets have the same surface gravity, but planet B has twice the radius of planet A. if planet A has mass m, what is the mass of planet B?

4m

When a box rests on a round sheet of wood on the ground, it exerts an average pressure p on the wood. If the wood is replaced by a sheet that has half the diameter of the original piece, what is the new average pressure?

4p

a solid cylindrical bar conducts heat at a rate of 25W from a hot to cold reservoir under steady state conditions. if both the length and the diameter of this bar are doubled, the rate at which it will conduct heat between these reservoirs will be

50W

the figure shows a 100 kg block being released from rest from a height of 1m. it then takes it 0.9s to reach the floor. what is the mass m of the other block? the pulley has no appreciable mass or friction.

60 kg

A certain gas is compressed adiabatically. The amount of work done on the gas is 800 J. What is the change in the internal (thermal) energy of the gas?

800J

Shown below are the velocity and acceleration vectors for a person in several different types of motion. in which case is the person slowing down and turning to his right?

A (acceleration NW, velocity S)

a cubical block of stone is lowered at a steady rate into the ocean by a crane, always keeping the top and bottom faces horizontal. which graph best describes the gauge pressure on the bottom of this block as a function of time if the block just enters the water at 0s?

A (positive slope, steep, starting at 0)

in the figure below a force is applied to a rod in several different ways. in which case if the torque due to F about the pivot P greatest?

A, how you push a door open

in the figure are scale drawings of 4 objects, each of the same mass and uniform thickness. which has the greatest amount of inertia when rotated about an axis perpendicular to the plane of the drawing?

B, the bike tire

a trolley starts from rest and runs down a sloping track section onto a second level section. which velocity-time graph represents the trolley's motion on both sections?

D (positive increasing slope, then levels out to slope=zero)

the plot below shows the position of an object as a function of time. the letters H-L represent particular moments of time. at which moment in time is the speed of the object equal to zero?

I (at the peak of the curve)

the oxygen molecules and the nitrogen molecules at any one place in our atmosphere are at the same temperature. how do the rms speeds of the 2 molecules compare?

N>O

a box of mass m is pulled with a constant acceleration a along a horizontal frictionless floor by a wire that makes an angle of 15 degrees about the horizontal. if T is the tension in this wire, then

T>ma

two objects, each of weight W, hang vertically by spring scales. the pulleys and the strings attached to the objects have negligible weight, and there is no appreciable friction in the pulleys. the reading in each scale is

W

in a collision between two objects having unequal masses, how does magnitude of the impulse imparted to the lighter object by the heavier one compare with the magnitude of the impulse imparted to the heavier object by the lighter one?

both objects receive the same impulse

you are standing on a skateboard, initially at rest. a friend throws a very heavy ball towards you. you can either catch the object or deflect the object back towards your friend (such that is moves away from you with the same speed as it was originally thrown). what should you do in order to minimize your speed on the skateboard?

catch the ball

a bimetallic strip, consisting of metal G on top of metal H on the bottom, is rigidly attached to a wall at the left. the coefficient of linear thermal expansion for metal G is greater than that of metal H. if the strip is uniformly heated, it will

curve downward

you hit a heavy box with a magnitude of force of 1500N. the magnitude of force the box exerts on you is

exactly 1500N whether or not the box moves

A car is being towed at constant velocity on a horizontal road using a horizontal chain. The tension in the chain must be equal to the weight of the car in order to maintain constant velocity.

false

If you swing a bucket of water fast enough in a vertical circle, at the highest point the water does not spill out. This happens because an outward force balances the pull of gravity on the water.

false

In order to get an object moving, you must push harder on it than it pushes back on you.

false

Since vectors always have positive magnitudes, the sum of two vectors must have a magnitude greater than the magnitude of either one of them.

false

a crate is sliding down an inclined ramp at a constant speed of 0.55m/s. the vector sum of all the forces acting on this crate must point down the ramp.

false

a heat engine that is 40% efficient and has a heat input of 200J per cycle at the hot reservoir will waste 80J of heat each cycle

false

if acceleration of an object is negative, the object must be slowing down

false

if the acceleration of an object is negative, the object must be slowing down

false

2 cyclists who weigh the same and have identical bikes ride up the same mountain, both starting at the same time. joe rides straight up the mountain, and bob rides up the longer the longer road that has a lower grade. joe gets to the top before bob. which is true?

ignoring friction and wind resistance, the amount of work done 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

the figure shows the velocity of a particle as it travels along the x-axis. what is the direction of the acceleration at t=0.5s?

in the -x direction

an air bubble is formed at the bottom of the lake, and begins rising toward the surface. the air is hotter than the water. if the temperature of the air remains constant as the bubble rises, the volume of the bubble will

increase

If the absolute temperature of an object is tripled, the thermal power radiated by this object will

increase by a factor of 81

an object is moving to the right, and experiencing a net force that is directed to the right. the magnitude of the force is decreasing with time. the speed of the object is

increasing

a person in a car is driving down a straight road. the instantaneous acceleration is decreasing with time, but is directed in the direction of the car's motion. the speed of the car is

increasing with time

the number of molecules in one mole of a substance

is the same for all substances

a piece of wood is floating in a bathtub. a second piece of wood sits on top of the first piece, and does not touch the water. if the top piece is taken off and placed in the water, what happens to the water level in the tub?

it does not change

A person ties a rock to a string and whirls it around in a vertical circle such that sometimes the rock is going straight upward and sometimes the rock is going straight down. She whirls the rock at the minimum speed (constant in time) such that the string is always taut (no sag). When is the tension the highest?

it is highest when the rock is at the lowest elevation

two identical stones are dropped from a tall building, one after the other. assume air resistance is negligible. while both stones are falling, what will happen to the vertical distance between them?

it will increase

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 in the x-direction is correct?

its acceleration is positive but its velocity is negative

a baseball is thrown vertically upward and feels no air resistance. as it is rising

its momentum is not conserved, but its mechanical energy is conserved

When a fixed amount of ideal gas goes through an isobaric expansion

its temperature must increase

two bodies P and Q on a smooth horizontal surface are connected by a light cord. the mass of P is greater than that of Q. a horizontal force F is applied to Q as shown in the figure, accelerating the bodies to the right. the magnitude of the force exerted by the connecting cord on the body P will be

less than F but not zero

a block is at rest on a rough incline. the magnitude of the frictional force acting on the block, along the incline, is

less than the weight of the block

a brick is resting on a rough incline. the friction force acting on the brick, along the incline, is

less than the weight of the brick

you are making a circular turn in your car when you hit a big patch of ice, causing the force of friction between the tires and the road to become zero. while the car is on the ice, it

moves along a straight-line path

Two men, Joel and Jerry, push against a wall. Jerry stops after 10 min, while Joel is able to push for 5.0 min longer. Compare the work they do.

neither of them does any work

a thermally isolated system is made up of a hot piece of aluminum and a cold piece of copper, with the aluminum and copper in thermal contact. the specific heat capacity of aluminum is more than double that of copper. which object experiences the greater magnitude gain or loss of heat during the time the system takes to reach thermal equilibrium?

neither one, both of them experience the same size gain or loss of heat

As a result of any natural process, the total entropy of any system plus that of its environment

never decreases

a ball is thrown vertically upward, reaches a highest point, and comes back down. at the top of its path, what forces, if any, act on the ball?

only a downward force

the average molecular kinetic energy of a gas can be determined by knowing

only the temperature of the gas

in figure, determine the character of the collision. before (4kg, 1.8m/s vs. 6kg, 0.2m/s) after (4kg, 0.6m.s vs. 6kg, 1,4m/s). the collision is

perfectly elastic

2 processes are shown on the pV diagram. one of them is an adiabat and the other is an isotherm. which is isotherm?

process A (curve not as steep)

A wooden block contains some nails so that its density is exactly equal to that of water. If it is placed in a tank of water and released from rest when it is completely submerged, it will

remain where it is released

a chunk of ice (T=-20C) is added to a thermally insulated container of cold water (T=0C). what happens in the container?

some of the water freezes and the chunk of ice gets larger

which is not a vector?

speed

a string is attached to the rear-view mirror of a car. a ball is hanging at the other end of the string. the car is driving around in a circle, at a constant speed. which of the following lists gives all of the forces directly acting on the ball?

tension and gravity

at a certain depth in the ocean, the absolute pressure is p. if you go twice that depth

the absolute pressure will be less than 2p

a ball is thrown directly upward and experiences no air resistance. which of the following statements about its motion is correct?

the acceleration is downward during the entire time the ball is in the air

the bernoulli effect is described by the equation that i don't feel like typing. the origin of this relation is that it is a statement of

the conservation of energy for a moving fluid

a merry-go-round is spinning with a fixed angular speed. as a person is walking towards the edge,

the force of static friction must increase in order for the person not to slide off

When a car goes around a circular curve on a horizontal road at constant speed, what force causes it to follow the circular path?

the friction force from the road

which contains more moles of material: 80g of He or 400g of Ar?

the helium

While an object is in projectile motion (with upward being positive) with no air resistance

the horizontal component of its velocity remains constant and the vertical component of its acceleration is equal to -g

suppose that a heavy person and a light person are balanced on a teeter-totter made of a plank of wood. each person now moves in toward the fulcrum a distance of 25cm. what effect will this have on the balance of the teeter-totter?

the light person's end will go down

Which of the following statements is true?

the magnitude of a vector is independent of the coordinate system used

the figure shows the position of an object (moving along a straight line) as a function of time. assume 2 significant figures in each number. which of the following statements about this object is true over the interval shown?

the object is accelerating to the left

the figure below shows the position of a particle (moving along a straight line) as a function of time. what is true?

the object is deaccelerating (slowing down)

an object has a velocity directed to the right, and an acceleration directed to the left. which is true?

the position of the object is increasing to the right with time, and its speed is decreasing

as shown in figure, fluid fills a container in several sections. at which point is pressure greatest?

the pressure is the same at each of the labeled points (horizontal line test)

an ideal gas inside box A of volume V has a temperature T and contains N molecules. an ideal gas inside box B of volume V/2 has a temperature T/2, and also contains N molecules. in which box is the pressure the highest?

the pressure is the same in both boxes

If you stood on a planet having a mass four times that of Earth's mass, and a radius two times that of Earth's radius, you would weigh

the same as you do on Earth

an object can slide without friction down 1 of 4 different ramps. the final elevation loss of each of the ramps is the same. neglecting friction, for which ramp will the speed of the object be the highest at the bottome?

the speed of the the ball will be the same for all ramps

a large truck collides head-on with a cyclist. during the collision

the truck exerts the same amount of force on the cyclist as the cyclist exerts on the truck

for general projectile motion, when the projectile is at the highest point of its trajectory

the velocity is perpendicular to the acceleration

a ball is tossed vertically upward. when it reaches its highest point (before falling back downward)

the velocity is zero, the acceleration is directed downward, and the force of gravity acting on the ball is directed downward

a cyclic process is carried out on an ideal gas such that it returns to its initial state at the end of the cycle. if the process is carried out in a clockwise sense around the enclosed area, then the magnitude of the enclosed area represents

the work done by the gas

3 cars 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 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 momemtum

A person stands on the edge of a cliff. She throws three identical rocks with the same speed. Rock X is thrown vertically upward, rock Y is thrown horizontally, and rock Z is thrown vertically downward. If the ground at the base of the cliff is level, which rock hits the ground with the greatest speed if there is no air resistance?

they all hit the ground with the same speed

bob and bill throw identical rocks off a tall building at the same time. bob throws his rock straight downward. bill throws his rock downward and outward such that the angle between the initial velocity of the rock and the horizon is 30 degrees. biff throws the rock with a speed twice that of bob's rock. which rock hits the ground first?

they hit at the same time

2 bullets are fired simultaneously parallel to a horizontal plane. the bullets have different masses and different initial velocities. neglecting air resistance, which one will strike the plane first?

they strike the plane at the same time

in figure, certain type of string will break is the tension in the string exceeds 300N. a number of 8kg weights are hung one below the other from a hook in the ceiling using this string. the number of weights that causes the string to break and the string segment that will break are as follows

when the 4th weight is added, the top string segment will break

Consider what happens when you jump up in the air. Which of the following is the most accurate statement?

when you push down on the earth with a force greater than your weight, the earth will push back with the same magnitude force and thus propel you into the air

if you set cruise control of your car to a certain speed and take a turn, the speed of the car will remain the same. is the car accelerating?

yes

a stalled car is being pushed up a hill at a constant velocity by three people. the net force on the car is

zero