Physics Exam 3

Three objects are moving along a straight line as shown in the figure. Taking the positive direction to be the right, what is the total momentum of this system?

-14.0 kg*m/s

A stone with a mass of 1.0 kg is tied to the end of a light string which keeps it moving in a circle with a constant speed of 4.0 m/s on a perfectly smooth horizontal tabletop. The radius of the path is 0.60 m. How much work does the tension in the string do on the stone as it makes one-half of a complete circle?

0 J

A 0.330 volleyball is thrown vertically downward with a speed of 0.150 m/s in a place where g=9.81 m/s2. it takes 0.0655 s to reach ground. What is the magnitude of its momentum just before it hits the ground?

0.262 kg*m/s

In a police ballistics test, 2.00 g bullet traveling 700m/s suddenly hits and becomes embedded in a stationary 5.00 kg wood block. What is the speed of the block immediately after the bullet has stopped moving relative to the block?

0.280 m/s

a 0.140 baseball is dropped and reaches a speed of 1.2 m/s just before it hits the ground and bounces. It rebounds with an upward velocity of 1.00 m/s. What is the change of the ball's momentum during the bounce?

0.308 kg.m/s upwards

How much work is required to stretch an ideal spring of a spring constant (force constant) 40 N/m from x=0.20 m to x=0.25m if the unstretched position is at x=0.0 m?

0.45 J

A 1.0 kg object moving in a certain direction has a kinetic energy of 2.0 J. It hits a wall and comes back with half its original speed. What I the kinetic energy of this object at this point?

0.50 J

A 0.14-kg baseball is dropped from rest from a height of 2.0 m above the ground. What is the magnitude of its momentum just before it hits the ground if we neglect air resistance?

0.88 Kg*m/s

a 35 N bucket of water is lifted vertically 3.0m and then returned to its original position. How much work did gravity do on the bucket during this process?

0J

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?

1

A 14,000 kg boxcar is coasting at 1.50 m/s along a horizontal track when it suddenly hits and couples with a stationary 10,000 kg boxcar. What is the speed of the car after collision?

1.143 m/s

a plastic block of dimensions 2cmx3cmx4cm has a mass of 30g. what is the density?

1.25 g/cm^3

The sun subtends an angle of 0.00928 rad when viewed from the surface of the earth, and its distance from earth is 1.5x10^11m what is the diameter of the sun?

1.4 x10^9

A 100-g ball falls from a window that is 12 m above ground level and experiences no significant air resistance as it falls. What is its momentum when it strikes the ground?

1.5 kg*m/s

calculate the pressure exerted on the ground due to the weight of the 68kg person standing on one foot. Bottom of foot is 13 cm wide and 28 cm long

1.8x10^4

A steel wire, 3.2 m long, has diameter of 1.2mm. Wire stretches 1.6mm when it bears a load. Young's modulus for steel is 2.0x10^11 Pa. The mass of the load is close to

12 kg

A force produces power P by doing work W in a time T. What power will be produced by a force that does six times as much work in half as much time?

12P

A bicycle has the wheels that are 60 cm in diameter. what is the angular speed of these wheels when its moving at 4.0 m/s

13 rad/s

A child pulls on a wagon with a force of 75 N. If the wagon moves a total of42 m in 3.1 min, what is the average power delivered by the child?

17 W

A uniform 40 N board supports 2 children weighing 500N and 350N. If the support is at the center of the board and the 500N child is 1.5 m from its center, how far is the 350 N child from the center?

2.1m

How many joules of energy are used by a 1.0 hp motor that runs for 1 hour?

2.7 MJ

A 1200 kg cannon suddenly fires a 100 kg cannonball at 33m/s. What is the recoil speed of the cannon?

2.8 m/s

Two astronauts, of masses 60 kg and 80 kg, are initially at rest in outer space. They push each other apart. How far has the heavier astronaut moved when the lighter has moved 12m?

21m

How much work would a child do while pulling a 12-kg wagon a distance of 4.3 m with a 22 N force?

26 J

A 1000-kg car experiences a net force of 9500 N while slowing down from 30 m/s to 19.0 m/s. How far does it travel while slowing down?

28 m

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?

2H

The diameter of the moon is 3.47x10^6m, and it subtends an angle of 0,00904 rad when viewed from the surface of earth. How far is the moon from earth?

3.84x10^8

A 4,0 kg cylinder of solid iron is supported by string while submerged in water. what is the tension of the string?

34N

A 3.0 kg brick rests on a perfectly smooth ramp inclined at 34 degrees above the horizontal. the brick is kept from sliding down the plane by an ideal spring that is aligned with the surface and attached to a wall above the brick. the spring has a spring constant of 120 N/m. By how much does the spring stretch with the brick attached?

360 cm

A tiger runs a straight line. If we double moth the mass and speed of the tiger, the magnitude of its momentum will increase by what factor?

4

If you want to double the momentum of a gas molecule, by what factor must you increase its kinetic energy?

4

A chicken is running in a circular path with an angular speed of 1.52 rad/s. How long does it take the chicken to complete one revolution?

4.13 s

a compressed gas with a total mass of 238 kg is stored in a spherical container having a radius of 0.521 m. what is the density of the compressed gas?

402 kg/m^3

An ideal spring with a spring constant (force constant) of 10 n/m is stretched from equilibrium to 2.9m. How much work is done in the process?

42 J

A 1000 kg car is moving at 15 km/h. If a 2000 kg truck has 22 times the kinetic energy of the car how fast is the truck moving?

50 km/h

A 12000 kg car moving at 15.5m/s suddenly collides with a stationary car of mass 1500 kg. If the 2 vehicles lock together, what is their combined velocity immediately after the collision?

6.9 m/s

A force of 54N stretches a very light spring 0.73 m from equilibrium. What is the force constant (spring constant) of the spring?

60 n/m

A 15-kg child is sitting on a playground teeter totter, 1.5 m from pivot. What is the magnitude of the minimum force, applied 0.3 m on the other side of pivot, that is needed to make a child lift off ground

740N

Through how many degrees does a 33 rpm turntable rate in .39 sec?

77

An empty train car of mass 2.0 x 10^4 kg coasts along at 10 m/s. A 3000 kg boulder is suddenly dropped vertically into the car. Find the speed of the car immediately after the boulder is dropped in

8.7 m/s

A batter applies an average force of 8000N to a baseball for 1.1 ms. What is the magnitude of the impulse delivered to the baseball?

8.8 n*s

What is the angular speed, in rad/s, of a flywheel turning at 813.0 rpm?

85.14 rad/s

A 12,000-N car is raised using a hydraulic lift, which consists of a U-tube with arms of unequal areas, filled with incompressible oil and capped at both ends with tight -fitting pistons. The wider arm of the U-tube has a radius of 18.0 cm and the narrower arm has a radius of 5.00 cm. The car rests on the piston on the wider arm of the U-tube. The pistons are initially at the same level. What is the initial force that must be applied to the smaller piston in order to start lifting the car? (For purposes of this problem, you can neglect the weight of the pistons.)

926 N

A scooter has wheels with a diameter of 120mm. What is the angular speed of the wheels when the scooter is moving forward at 6.00 m/s?

955 rpm

A heavy stone and a light stone are released from rest in such a way that they both have the same amount of gravitational potential energy just as they are released. Air resistance is negligibly small. Which of the following statements about these stones are correct? (there could be more than one correct answer)

A) The initial height of the light stone is greater than the initial height of the heavy stone. D) Just as it reaches the ground, the light stone is traveling faster than the heavy stone. E) The stones both have the same kinetic energy just as they reach the ground.

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.)

Ahmed has a greater tangential speed than Jacques

The figure shows scale drawings of four objects, each has same mass and thickness, with mass distributed uniformly. Which one has the greatest amount of inertia?

B (bicycle tire looking one)

Three cars (car L, car M, and car N) are moving with the same speed and slam on their brakes. The most massive car is car L, and the least massive is car N. If the tires of all three cars have identical coefficients of kinetic friction with the road surface, for which car is the amount of work done by friction in stopping it the greatest?

Car L

The graphs shown show the magnitude F of the force exerted by a spring as a function of the distance x the spring has been stretched. For which one of the graphs does the spring obey Hooke's law?

Graph B (moves up constantly)

A spinning ice skater on smooth ice is able to control the rate at which she rotates by pulling in her arms. which of the following statements are true about the skater during this process?

Her angular momentum remains constant

Which of the following quantities are units of impulse?

N*s Kg*m/s

An ornament of mass 40.0 g is attached to a vertical ideal spring with a force constant (spring constant) of 20.0 N/m. The ornament is then lowered very slowly until the spring stops stretching. How much does the spring stretch?

O.0196 m

When is the angular momentum of a system constant?

Only when no net external torque acts on the system.

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 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

Two equal-magnitude forces are applied to a door at the doorknob. The first force is applied perpendicular to the door, and the second force is applied at 30° to the plane of the door. Which force exerts the greater torque about the door hinge?

The first force (applied perpendicular to the door)

A rubber ball bounces off a wall with initial speed V and reverses its direction so its speed is v right after the bounce. AS a result of the bounce, which of the following quantities of the ball are conserved?

The kinetic energy of the ball

Two objects of different masses have momentum of equal, non-zero magnitude. Which object has more kinetic energy?

The lighter object

As shown in the figure, fluid fills a container having several sections. At which of the indicated points is the pressure greatest?

The pressure is the same at each of the points

A rocket explodes into two fragments, one 25 times heavier than the other. The magnitude of the momentum change of the lighter fragment is

The same as the momentum change of the heavier fragment

A stone can slide down one of four different frictionless ramps, as shown in the figure. For which ramp will the speed of the ball be the greatest at the bottom?

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

When a rigid object rotates about a fixed axis, what is true about all the points in the object?

They all have the same angular acceleration the the same angular speed

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 with no air resistance. Which object rises to a greater height?

They both slide to exactly the same height

A centrifuge in a medical laboratory rotates at a rotational speed of 3600 rev/min. It takes 50 complete turns at constant acceleration before rest. a) what is the magnitude of the angular acceleration of the centrifuge as it slowed down? b)how long did it take for the centrifuge to come to rest after turned off?

a) 226.20 rad/sec^2 b)1.7 sec

As you are leaving a building, the door opens outward. If the hinges on the door are on your right, what is the direction of the angular velocity of the door as you open it?

down

A boat loaded with rocks is floating in a swimming pool. If the rocks are thrown into the pool, the water level in the pool

falls

If the sum of the external forces on an object is zero, then the sum of the external torques on it must also be zero.

false

A steel ball sinks in water but floats in a pool of mercury. Where is the buoyant force on the ball greater?

floating on the mercury

Jill does twice as much work as Jack does and in half the time. Jill's power output is

four times Jack's power output

Consider a brick that is totally immersed in water, with the long edge of the brick vertical. The pressure on the brick is

greatest on the bottom of the brick

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 angular speed decreases

A railroad car collides with and sticks to an identical railroad car that is initially at rest. After a collision, the kinetic energy of the system

is half as much as before

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

As a rock sinks deeper and deeper into water of constant density, what happens to the buoyant force on it?

it first increases and then remains constant

Which of the following are SI units of Young's modulus?

kg/m*s^2

A solid sphere and a solid cylinder, both uniform and of the same mass and radius, roll without slipping at the same forward speed. It is correct to say that the total kinetic energy of the solid sphere is

less than total kinetic energy of the cylinder

If a quantity you calculated had units of kg*m/s what type of quantity could it be?

momentum impulse

Two men, Joel and Jerry, push against a car that has stalled, trying unsuccessfully to get it moving. Jerry stops after 10 min, while Joel is able to push for 5.0 min longer. Compare the work they do on the car.

neither of them does any work

A hollow sphere of negligible mass and radius R is completely rilled with a liquid so that its density is p. You now enlarge the sphere so tis radius is 2R and completely fill it with liquid. What is the density of enlarged sphere?

p

In the figure, determine the character of the collision. the masses of the blocks, and the velocities before and after, are shown. The collision is

perfectly elastic

If the units of your answer are kg•m2/s3, which of the following types of quantities could your answer be? (There could be more than one correct choice.)

power

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

When you throw a pebble straight up with initial speed V, it reaches a maximum height H with no air resistance. At what speed should you throw it up vertically so it will go twice as high?

square root of 2 V

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

Salt water has greater density than fresh water. A boat floats in both fresh water and in salt water. Where is the buoyant force greater on the boat?

the buoyant force is same in both cases

A disk and a hoop of the same mass and radius are released at the same time at the top of an inclined plane. If both are uniform, which one reaches the bottom of the incline first if there is no slipping?

the disk

Two objects, one of mass m and the other of mass 2m, are dropped from the top of a building. If there is no air resistance, when they hit the ground

the heavier one will have twice the kinetic energy of the lighter one

A waiter fills your water glass with ice water (containing many ice cubes) such that the liquid water is perfectly level with the rim of the glass. As the ice melts,

the liquid-water level remains flush with the rim of the glass

A merry-go-round spins freely when Diego moves quickly to the center along a radius of the merry go round. AS he does this,

the moment of inertia of the system decreases and the angular speed increases

As one stretches a metal wire, which condition is reached first?

the proportional unit

Which one of the following is an accurate statement?

the ratio of tensile stress to tensile strain is called Young's modulus

A small car meshes with a large truck in a head-on collision. Which of the following statements concerning the magnitude of the average collision force is correct?

the small car and the truck experience the same average force

Three cars (car F, car G, and car H) are moving with the same speed and slam on their brakes. The most massive car is car F, and the least massive is car H. If the tires of all three cars have identical coefficients of kinetic friction with the road surface, which car travels the longest distance to skid to a stop?

they all travel the same distance when stopping

In a collision between two unequal masses, which mass receives a greater magnitude impulse?

they receive equal impulses

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

to your left

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

Swimmers at a water park have a choice of two frictionless water slides, as shown in the figure. Although both slides drop over the same height h, slide 1 is straight while slide 2 is curved, dropping quickly at first and then leveling out. How does the speed v1 of a swimmer reaching the bottom of slide 1 compare with v2, the speed of a swimmer reaching the end of slide 2?

v1=v2

The graph in the figure shows the tensile stress as a function the the tensile strain in a certain wire. What does the slope of this graph give us for this wire?

young modulus for the material of the wife