Physics Exam 2

The radius of the aorta is ~ 10 mm = 10-2 m and the blood flowing through it has a speed ~ 300 mm/s = 0.3 m/s. A capillary has a radius ~ 4×10-3 mm = 4×10-6 m, but there are literally billions of them. The average speed of blood through the capillaries is ~ 5×10-4 m/s. (i) Calculate the effective cross sectional area of the capillaries and(ii) the approximate number of capillaries.

(i) 0.188 m2, (ii) 3.75*109

A centrifuge in a medical laboratory rotates at an angular speed of 3600 rev/min. When switched off, it rotates 50 times before coming to rest. What is the constant angular acceleration of the centrifuge?

-226.2/s^2

Consider a 100 kg father and his 20 kg girl. They decide to enjoy balancing on a seesaw, which is a uniform board 4 m long and pivoted exactly at its center. If girl sits at the seesaw's end (2m from the center), how far from the center on the other side should the father sit?

0.4m

An intravenous blood plasma drip enters a vein in the patient's arm from a bag raised a height h above the vein. If the diameter of the 5 cm long needle is 0.5 mm, use Poiseuille's law to find the height h that results in a 5 cm3/min flow rate.(Assume the blood pressure in the arm is 18 torr = 2392 Pa and the viscosity of the blood plasma is 1.5*10-3 Pa-s.)

0.66 m

Suppose the flow rate of blood in a coronary artery has been reduced to 0.488 times its normal value by plaque deposits, and that the pressure difference across the artery has not changes. By what factor has the radius of the artery been reduced, assuming no turbulence occurs? Enter a number with three digits behind the decimal point.

0.836

The volume flow rate of water through a horizontal pipe is 1.1 m3/min. Determine the speed of flow (in m/s) at a point where the diameter of the pipe is 15.1 cm. Enter a number with two digits behind the decimal point.

1.02

Two masses are located on the x-axis. Mass m1 = 4 kg is located at x = -50 cm and mass m2 = 6 kg is located at x = 20 cm. What is the moment of inertia of the system about the z-axis in units of kgm2.

1.24

The volume flow rate of water through a horizontal pipe is 3.5 m3/min. Determine the speed of flow (in m/s) at a point where the diameter of the pipe is 20 cm. Enter a number with two digits behind the decimal point.

1.86

You live in an apartment directly above an open-air tavern and you possess a really, really long and sturdy straw. You plan to steal beer by leaning out of your apartment window and, when the beer-drinkers are not looking, sticking your straw into beer glasses and sucking on the straw. Assuming you can create a perfect vacuum when you suck on the straw, for this plan to have a chance of working, the height difference between you and the beer must be less than approximately what distance? (Assume the density of beer is equal to the density of water and the pressure is 1 atm = 101 kPa.)

10 m

A 500 N weight sits on the small piston of a hydraulic machine in equilibrium. The small piston has area 2.0 cm2. If the large piston has area 40 cm2, how much weight does the large piston support?

10000 N

Let g = 9.8 m/s2. A hydraulic system is used to lift a 56 kg motor in a garage. If the motor sits on a piston of area 0.24 m2, and a force is applied to a piston of area 63 cm2, what is the minimum force that must be applied to lift the motor in units of N? Enter a number with one digit behind the decimal point.

14.4

Two blocks of mass M and 3 M are placed on a horizontal frictionless surface. A light spring is attached to one of them, and the blocks are pushed together with the spring between them. A cord holding them together is burned, after which the block of mass 3 M moves to the right with a speed of 5 m/s. What is the speed of the block of mass M?

15 m/s to the left

A 3.9 kg object has kinetic energy 3,162 J. What is the magnitude of its momentum (in kg m/s)?

157

Suppose you are changing a car tire and loosening a lug nut. You weigh 800 N and stand on the end of a horizontal 2 m long wrench. How much torque do you exert on the lug nut?

1600 Nm

A 2 kg block of wood is floating in water. What is the magnitude of the buoyant force acting on the block?

19.6 N

A bicycle's wheels have a radius of 33 cm. The bicycle is traveling at a speed of 6.5 m/s. What is the angular speed of the front tire?

19.7

A 1 kg rock is suspended by a massless string from one end of a meter stick at the 0 cm mark. What is the mass m suspended from the meter stick at the 75 cm mark if the system is balanced?

2 kg

Suppose the circumference of a bicycle wheel is 2 m. If it rotates at 1 revolution per second when you are riding the bicycle, then your speed will be

2 m/s

A 0.6 kg toy car moving in the positive x direction with speed 3 m/s hits a toy car of equal mass moving in the positive y-direction with speed of 2.8 m/s. If the collision is perfectly inelastic, calculate the speed of the cars (in m/s) right after the collision. Enter a number with one digit after the decimal point.

2.1

A fan rotating with an initial angular velocity of 1000 rev/min is switched off. In 2 seconds, the angular velocity decreases to 200 rev/min. Assuming the angular acceleration is constant, how many revolutions does the blade undergo during this time?

20

In SI units, what is the change in the magnitude of the momentum of a 1,823 kg car that accelerates uniformly along a straight line from a speed of 8 m/s to a speed of 19 m/s in 6 s?

20053

A wheel with moment of inertia 0.05 kgm2 rotates about a fixed axis. Its kinetic energy is 1,374 J. What is ts angular speed ω in s-1? Enter an integer.

234

In SI units, what is the magnitude the net force acting on a 1,767 kg car that accelerates uniformly along a straight line from a speed of 8 m/s to a speed of 20 m/s in 9 s?

2356

Blood is pumped from the heart at a volume flow rate of 5.0 liter/min into the aorta (of radius 1.0 cm). Determine the speed of blood through the aorta.

26.5 cm/s

A 31 kg object is placed on a 111 cm2 platform. What is the pressure the object exerts on the platform in N/m2? Let g = 9.8 m/s2. Enter an integer.

27369

A 44 kg object is placed on a 150 cm2 platform. What is the pressure the object exerts on the platform in N/m2? Let g = 9.8 m/s2. Enter an integer.

28747

A centrifuge starts from rest. Its angular acceleration α is constant for 12 s.Its final angular speed is ω = 58 revolutions per second.What is its angular acceleration α in units of s-2? Enter a number with one digit behind the decimal point

30.4

Mercury has an unusually large surface tension γ = 0.465 N/m. Calculate the excess pressure inside a drop of mercury 4 mm in diameter.

465 Pa

Substance A has a density of 3.0 g/cm3 and substance B has a density of 4.0 g/cm3. In order to obtain equal masses of these two substances, the ratio VA/VB of the volume of A to the volume of B has to be equal to

4:3

An object rotates initially with a period of 1.0 s. It accelerates with constant angular acceleration for 10 s. Its final rotation period is 0.1 s.What was the magnitude of its angular acceleration?

5.65

A CD spins at 5500 rpm (revolutions per minute). What is its angular speed in units of rad/s or s-1?

576

A 50 kg woman balances on one heel of a high-heel shoe. If the heel is circular with radius 0.5 cm, what pressure does she exert on the floor?

6.2 MPa

A 2 kg mass is at x = 0 m, y = 2 m, and a 3 kg mass is at x = 2 m, y = 0 m. The x- and y-coordinates, respectively, of the center of mass of this system are

6/5 m, 4/5 m

You are bored during the summertime when school is not in session and you decide to do an experiment where you compare the properties of water and air. If the density of air is 1.25 kg/m3 and the density of water is 1000 kg/m3, what volume of air weighs the same as 1 liter (10-3 m3) of water?

800 liters

The diameter of a pipe is tripled while the pressure difference across the pipe remains the same. The volume flow rate of the pipe increases by a factor of

81

Fluid is flowing from left to right through the pipe. Points A and B are at the same height, but the cross-sectional areas of the pipe differ. Points B and C are at different heights, but the cross-sectional areas are the same. Rank the pressures at the three points, from highest to lowest.

A, B, C

Which of the following statements is false? A. Plaque deposit on an artery or arteriole wall causes an increase in local blood pressure and can lead to bursting of that vessel. B. Plaque deposit on an artery or arteriole wall can lead to the collapse of that vessel. C. Plaque deposit on an artery or arteriole wall leads to a decreased local blood pressure. D. The speed of the blood increases as it moves through a region of an artery with plaque deposit. E> An aneurysm in an artery leads to a locally elevated blood pressure.

A. Plaque deposit on an artery or arteriole wall causes an increase in local blood pressure and can lead to bursting of that vessel.

Which of the following assumptions is not made in the derivation of Bernoulli's equation? A. There is negligible gravity. B. There is negligible friction. C. There is no turbulence. D. There is negligible viscosity. E. Streamlines do not cross.

A. There is negligible gravity.

Two cars move towards each other on a frictionless road as shown in the sketch below.The two cars collide and immediately come to a standstill.During the collision, the total momentum of the two vehicles will A. stay constant. B. first increase and then decrease. C. first decrease and then increase. D. decrease.

A. stay constant.

The vessels shown below all contain water to the same height.Rank them according to the pressure exerted by the water on the vessel bottoms, least to greatest.

All pressures are the same.

Consider the earth spinning from west to east on its axis. It is slowing down in its rotation due to friction with the air. Using the right hand rule, in what direction is the frictional torque? A. S pole to N pole B. N pole to S pole C. Counterclockwise along the equator D. Clockwise along the equator

B. N pole to S pole

Two moving objects have masses m1 and m2, respectively. If m2 = 4m1, and both have the same kinetic energy, which has more momentum? A. Object 1 with mass m1. B. Object 2 with mass m2. C. Both objects have the same momentum. D. No relationship between kinetic energy and momentum exists.

B. Object 2 with mass m2.

Blood flows through a section of a horizontal artery that is partially blocked by a deposit along the artery wall. A hemoglobin molecule moves from the narrow region into the wider region. What happens to the pressure acting on the molecule as it moves from the narrow to the wider region? A. The pressure decreases. B. The pressure increases. C. There is no change in the pressure.

B. The pressure increases.

The left tip of a wind turbine blade accelerates upward, as you view it. By the right-hand rule, the torque on the wind turbine is pointing A. up. B. away from you. C. toward you. D. down. E. counterclockwise.

B. away from you.

During a football game the ball is kicked and it travels across the field. If the ball is kicked away from its center of mass it will A. only have translational motion. B. have translational and rotational motion. C. only have rotational motion. D. only have vibrational motion.

B. have translational and rotational motion.

The quantities remain constant in an inelastic collision are A. momentum and temperature but not kinetic energy. B. momentum, but neither kinetic energy nor temperature. C. momentum and kinetic energy but not temperature. D. momentum, kinetic energy and temperature. E. neither kinetic energy nor momentum, nor temperature.

B. momentum, but neither kinetic energy nor temperature.

A skater who is spinning and throws her arms out slows down because A. she exerts less torque. B. she makes her rotational mass or moment of inertia bigger. C. she makes her rotational mass or moment of inertia smaller. D. she increases friction.

B. she makes her rotational mass or moment of inertia bigger.

Compared to a gear tooth on the rear sprocket (on the left, of small radius) of a bicycle, a gear tooth on the front sprocket (on the right, of large radius) has A. the same linear speed and a faster angular speed. B. the same linear speed and a slower angular speed. C. a slower linear speed and the same angular speed. D. a faster linear speed and a faster angular speed

B. the same linear speed and a slower angular speed.

The picture below shows 5 blocks. The blocks have equal volumes but different masses. The blocks are placed in an aquarium tank filled with water and blocks 2 and 5 come to rest as shown in the figure. Which answer is correct?

Block 3 will come to rest in the same position as block 5.

You need to loosen a very tight bolt. You have one wrench and you exert maximum force. Which configuration shown below gives you maximum chance of success?

C

In soap box car races, the cars are boxes with wheels. They begin at rest at the top of a hill, and at the start of the race they all begin rolling down the hill. The soap box car that reaches the bottom of the hill first is the winner. You have entered a soap box car race where the rule is that all the wheels and cars must have equal mass. Since you have taken Physics, you know that it is worse to have wheels with spokes (where the mass is mostly on the rim) rather than solid wheels because A. The solid wheels are easier to paint. B. The solid wheels have a higher rotational mass or moment of inertia and therefore will retain more rotational energy. C. Given the same torque, the wheels with spokes have a higher rotational mass or moment of inertia and therefore will have a smaller angular acceleration. D. Given the same torque, the wheels with spokes have a higher rotational mass or moment of inertia and therefore will have a greater angular acceleration. E. Given the same amount of energy, too small a fraction is converted into rotational kinetic energy of the wheels.

C. Given the same torque, the wheels with spokes have a higher rotational mass or moment of inertia and therefore will have a smaller angular acceleration.

A block and a rod are joined together. Each object is of uniform density. The center of mass of the combined object is at the position shown by the "X."Which has the greater mass, the block or the rod? A. The rod has the greater mass. B. The block and the rod have the same mass. C. The block has the greater mass. D. Not enough information is given to decide

C. The block has the greater mass.

An ideal, non-compressible fluid is used in the system of pipes shown below. The cross sectional area of pipe 1 is 4 m2, that of pipe 2 is 3 m2, and that of pipe 3 is 2 m2. The fluid enters pipe 1 at 2 m/s, and leaves pipe 2 at 3 m/s. What is the speed of the fluid in pipe 3 and in which direction does it flow? A. The fluid enters pipe 3 (upward) with speed 1 m/s. B. The fluid enters pipe 3 (upward) with speed 0.5 m/s. C. The fluid leaves pipe 3 (downward) with speed 0.5 m/s. D. The fluid leaves pipe 3 (downward) with speed 2 m/s. E. The fluid enters pipe 3 (upward) with speed 2 m/s.

C. The fluid leaves pipe 3 (downward) with speed 0.5 m/s.

A boat is floating in a lake. Since it is floating the buoyant force acting on the boat must be A. zero. B. greater than its weight. C. equal to its weight. D. less than its weight.

C. equal to its weight.

Suppose you have two containers with liquid in them. One has a density of 760 kg/m3 and the other has a density of 910 kg /m3. If an object floats in one container and sinks in the other, the density of the object A. must have a value equal to the average densities of the two liquids. B. has a value greater than 910 kg/m3. C. has a value between 760 kg/m3 and 910 kg/m3. D. has a value less than 760 kg/m3. E. has a value equal to the difference in densities of the two liquids.

C. has a value between 760 kg/m3 and 910 kg/m3.

During a football game the ball is kicked and it travels across the field. If the ball is kicked away from its center of mass it will A. only have vibrational motion. B. only have translational motion. C. have translational and rotational motion. D. only have rotational motion.

C. have translational and rotational motion.

It is correct to say that impulse is equal to A. the force multiplied by the distance the force acts. B. work. C. the change in momentum. D. momentum.

C. the change in momentum.

When blood flows into an aneurysm A. the speed increases and the pressure increases. B. the speed decreases and the pressure decreases. C. the speed decreases and the pressure increases. D. the speed increases and the pressure decreases.

C. the speed decreases and the pressure increases.

Two carts A and B are moving towards each other as shown in the diagram. They collide and come to rest at the point of impact. From this observation we can conclude that the carts A. were moving with equal kinetic energies. B. collided elastically. C. were moving with momenta equal in magnitude and opposite in direction. D. were moving with velocities equal in magnitude and opposite in direction. E. have equal masses.

C. were moving with momenta equal in magnitude and opposite in direction.

In a stationary homogeneous liquid near the surface of Earth, which of the following is true? A. Pressure is independent of any atmospheric pressure on the upper surface of the liquid. B. Pressure is largest near the top of the liquid. C. Pressure is the same at all points independent of depth. D. Pressure is the same at all points at the same height. E. Pressure depends on the direction.

D. Pressure is the same at all points at the same height.

A boat floating in a lake contains a block of volume V0. The density of the block is 5000 kg/m3. If the block is thrown overboard, the volume of the water displaced by the block is A. 5V0. B. 0. C. 4V0. D. V0. E> V0/5.

D. V0.

A man, with his arms at his sides, is spinning on a light frictionless turntable. When he extends his arms A. his angular velocity increases. B. his angular momentum decreases. C. his angular velocity remains the same. D. his angular momentum remains the same. E. his moment of inertia decreases.

D. his angular momentum remains the same.

Rockets receive their forward propulsion through A. mass conservation of the rocket and fuel. B. pushing against the ground and objects in space. C. turbojet engines. D. pushing against the exhaust. E. small aerodynamic forces.

D. pushing against the exhaust.

If you dangle two pieces of paper vertically a few inches apart and blow air between them A. the papers will remain vertical. B. the papers will move apart because the air pressure exerts an outward force. C. the papers will move apart because the air friction causes an increased pressure. D. the papers will move together because the increased velocity reduces the pressure between the papers. E. the papers will move together because they become sticky.

D. the papers will move together because the increased velocity reduces the pressure between the papers.

A beaker is filled with water to the rim. Gently you place a toy duck in the beaker and some of the water spills out. The duck floats. The weight of the beaker with the duck floating in it is A. greater or less than its weight before adding the duck, depending on the weight of the duck. B. less than its weight before adding the duck. C. greater than its weight before adding the duck. D. the same as its weight before adding the duck.

D. the same as its weight before adding the duck.

Why do elastic balls bounce so well? A. They permanently deform, storing energy. B. They are always thrown well. C. They are all filled with a special energy-absorbent liquid. D. They get energy from the floor. E. They store energy through compression, like a spring.

E. They store energy through compression, like a spring.

Suppose you work in the E.R. and a choking patient comes in with their trachea half obstructed. (The diameter is half of what it was before the obstruction.) You manage to correct the problem and send them on their way safely, explaining that such obstructions are particularly dangerous because A. a half - blocked airway passes only 1/2 the regular amount of air. B. a half - blocked airway passes only 1/32 the regular amount of air. C. a half - blocked airway passes only 1/8 the regular amount of air. D. a half - blocked airway passes only 1/4 the regular amount of air. E. a half - blocked airway passes only 1/16 the regular amount of air.

E. a half - blocked airway passes only 1/16 the regular amount of air.

After clearing the bar on a high jump, you land softly on a giant mattress. Landing on a mattress is more comfortable than landing on a sand heap of equal size because A. you transfer less energy to the mattress in coming to a stop than you would have transferred to the sand heap. B. you transfer less momentum to the mattress in coming to a stop than you would have transferred to the sand heap. C. you transfer more momentum to the mattress in coming to a stop than you would have transferred to the sand heap. D. your velocity is less as you land on the mattress than it would be if you landed on the sand heap. E. the force the mattress exerts on you to stop your descend is much less than the force the sand heap would exert on you.

E. the force the mattress exerts on you to stop your descend is much less than the force the sand heap would exert on you.

It is possible for two objects of equal mass to have different moments of inertia about the same axis because A. the moment of inertia is always half the square of the angular speed. B. one object may not be rotating and therefore have no moment of inertia. C. the moment of inertia is always half the angular speed. D. the objects may be made out of different materials. E. the moment of inertia depends on the total mass and the mass distribution.

E. the moment of inertia depends on the total mass and the mass distribution.

Suppose you have an aquarium. You have a solid plastic decoration and a rock of about the same volume but the rock has twice the mass. Both are totally submerged in the water. The buoyant force on the plastic object is about A. one half as big as that on the rock. B. twice as big as that on the rock. C. four times as big as that on the rock. D. one quarter as big as that on the rock. E. the same as that on the rock.

E. the same as that on the rock.

Modeling a meter stick as a forearm, compare the force FB that the biceps has to exert to keep the forearm horizontal to the weight of the forearm FW = mg. Let d = 10 cm and the distance from where the biceps muscle attached to the center of mass be d' = 40 cm.

FB = 5 mg

Consider two masses, each of size 2m at the ends of a light rod of length L with the axis of rotation through the center of the rod. The rod is doubled in length and the masses are halved. Compare IA and IB.

IA < IB

A DVD is rotating with an ever increasing speed. How do the angular velocity, angular acceleration, tangential velocity, and tangential acceleration compare at points P and Q? A. Points P and Q have the same angular velocity and the same angular acceleration. B. Points P and Q have the same angular velocity but point Q has a larger angular acceleration. C. Points P and Q have the same tangential velocity and the same tangential acceleration. D. Angular velocity, angular acceleration, tangential velocity, and tangential acceleration are larger for point Q than for point P. E. Point Q has a larger tangential acceleration but points P and Q have the same tangential velocity.

Points P and Q have the same angular velocity and the same angular acceleration.

Suppose you are on a cart, initially at rest on a frictionless, horizontal track. You throw a series of identical balls against a wall that is rigidly mounted to the cart. If the balls are thrown at a steady rate and bounce straight back, is the cart put into motion?

Yes, it starts to move to the left with constant speed.

The shape of a droplet of liquid on a surface is due to a combination of

adhesion and cohesion

The SI units for viscosity are...

kg/(m-s)

A person sips a drink through a straw. At which of the following three positions is the pressure lowest? I. Inside the person's mouth II. At the surface of the drink III. At the bottom of the drink

only at position 1

One kilogram of iron (density ~7.8 gm/cm3) and 1 kilogram of aluminum (density ~2.7 gm/cm3) are dropped into a pool. Which is acted on by the largest buoyant force?

the aluminum

It is correct to say that impulse is equal to

the change in momentum