Physics midterm

A cue ball strikes an eight ball of an equal mass, initially at rest. The cue ball stops and the eight ball moves forward with a velocity equal to the initial velocity of the cue ball. What type of collision is this?

elastic

A box is pushed across a rough horizontal floor by a force acting parallel to the floor in the direction of motion. A force doing negative work on the body is

friction

The impulse required to bring an auto to a stop is ordinarily provided by __________________ forces.

frictional

A sports car accelerates rapidly from a stop and "burns rubber." What energy transfers occur in this situation? Select all that apply.

fuel to kinetic energy fuel to heat

Suppose that on a perfectly still day, a sailboat enthusiast decides to bring along a powerful battery-operated fan in order to provide an air current for his sail, as shown in the diagram. Would the sailor be better off with the sail furled (down) or unfurled (up)?

furled

Suppose that you move your hand forward to meet the egg when performing the egg-toss game. Will this be more, less or equally likely to break the egg than moving your hand backwards?

more

A railroad car collides and couples with a second railroad car that is standing still, and the two stick together. What type of collision is it?

completely inelastic

A car moves along a straight section of road so that its velocity varies with time as shown in the graph. At which of the labeled points on the graph, A, B, or C, is the magnitude of the acceleration greatest?

during segment A

A rectangular block is suspended by a string in a beaker of water so that the block is completely surrounded by water. How does the water pressure at the bottom of the block compare with the water pressure at the top of the block?

greater at the bottom

In which situation is the average speed most likely to be equal to the instantaneous speed?

in free-flowing, low-density traffic

Two masses, m1 and m2, connected by a string, are placed upon a fixed frictionless pulley as shown in the diagram. Match the situation the left with the effect on the left.

m1>m2- m1 accelerate downwards m1=m2- no acceleration m1<m2- m2 accelerates downwards

A ball bounces off a wall that is rigidly attached to the Earth. Is the momentum of the ball conserved in this process?

no

Are impulse and force the same thing?

no

Two lumps of clay, equal in mass, are traveling through the air at right angles to each other with velocities of equal magnitude. They collide and stick together. Is it possible that their velocity vector after the collision is in the direction shown in the diagram?

no

If a force acts on an object, the impulse will be

nonzero

Why are bicycle tires often inflated to a higher pressure than automobile tires, even though automobile tires must support a much larger weight?

the area of contact of the bicycle tires is smaller

If a ball is whirled in a vertical circle with constant speed, at what point in the circle, if any, is the tension in the string greatest?

the bottom of the circle

A driver steps on the brakes, causing the velocity of the car to decrease. Which of the following statements is correct?

the driver has accelerated

A man pushes off a wall and slides across a wooden floor, slowing down as he travels. Which forces act and do work on the man?

the friction force

Two ice skaters, initially at rest push off one another. What sign is the total momentum of the system after they push off?

zero

If a world-class sprinter ran a distance of 280 m starting at his top speed of 27 m/s and running with constant speed throughout, how long would it take him to cover the distance?

10.37s

A painter of mass 70 kg climbs 3.0 m up a ladder. The painter's potential energy has increased by

2058 J

A car starts from rest and reaches 20 m/s in 5 seconds. The average acceleration of the car is

4.0 m/s2.

Two forces, A = 75 N and B = 36 N, act in opposite directions on a box, as shown in the diagram. What is the mass of the box if its acceleration is 8 m/s2?

4.88kg

An auto, starting from rest, undergoes constant acceleration and covers a distance of 1250 meters. The final speed of the auto is 50 meters/sec. How long does it take the car to cover the 1250 meters?

50 s

Dylan has a weight of 800 N when he is standing on the surface of the Earth. What would his weight (the gravitational force due to the Earth) be if he tripled his distance from the center of the Earth by flying in a spacecraft? (Round the final answer to four decimal places.) His weight would be ____________ N when the distance from the center of the Earth is tripled.

88.8889 N

In this diagram a force acting on a block is shown by the arrow labeled F. The mass of the block is known, as is the size of the force, but the observed acceleration is larger than F/m and so another force must act on the block. In which direction (A, B, C, or D) is this force?

D

The velocity-vs-time graph of an object curves as shown in the diagram. Is the acceleration of the object constant? -on a curve

No

An average force of 4800 N acts on a golf ball for a time interval of 0.007 s

The magnitude of the impulse acting on the golf ball is 33.6 Ns

The acceleration due to gravity on the moon is approximately one-sixth the gravitational acceleration near the Earth's surface. If a rock is transported from the Earth to the moon which of the following will occur?

The mass of the rock will remain the same while its weight will decrease.

A car goes around a curve traveling at constant speed. Which of the following statements is correct? Check all that apply

The net force on the car is not zero. The acceleration of the car is not zero.

How is the mass of an object different from its weight?

The weight of an object is the amount of force exerted on the object by gravity while the mass is the amount of matter in the object.

In the case of uniform accelerated motion, the graph of velocity versus time is a straight line.

True

In which of the following systems is the work done by a frictional force resulting in the increase of the total mechanical energy of a system?

a car with positive acceleration

You have three carts connected by strings, as shown in the diagram. Assume their masses M1 , M2 , M3 are different from one another. If the acceleration of M1 is called a1 , the acceleration of M2 is called a2 and the acceleration of M3 is called a3 which of the following correctly states the relative size of each masses acceleration?

a1 = a2 = a3

A quantity that is a measure of how the velocity of a body changes with time is

acceleration

For a real world pendulum is the total mechanical energy conserved?

almost, only a small amount is lost to friction

The highway patrol sometimes uses radar guns to identify possible speeders and at other times uses associates in places who note the time taken for a car to pass between two marks some distance apart on the highway. Match each measurement method with what they are measuring.

average speed- plane, instantaneous speed- radar

A car traveling at constant speed

can change direction.

Acceleration represents the

change in velocity with respect to time.

Average speed is calculated by

dividing the distance traveled by the elapsed time.

A pendulum is pulled back from its equilibrium (center) position and then released. What form of energy is added to the system prior to its release?

gravitational potential energy

Car A travels with speed v around curve number one, which has a radius r. Car B travels with speed 2v around curve number two, which has a radius 2r. The acceleration will be

greater for car B.

Under what traffic conditions is the average speed of several vehicles equal to the average speed of the individual vehicles within the group?

high density highway traffic jam

When a bow and arrow are cocked, a force is applied to the string in order to pull it back. How does the total energy of the system change, if it does?

increases

From a graph of speed versus time, like Figure 2.15, for a body sliding down a ramp, one can get the _______________ ____________________ from the slope of the curve.

instantaneous acceleration

A car moves along a straight section of road so that its velocity varies with time as shown in the graph. During which segment does the car go backwards?

it does not go backwards during any segments

If a ball bounces off a wall so that its velocity coming back has the same magnitude that it had prior to bouncing. how has the momentum of the ball changed?

its direction has changed

The basic unit of mass is the

kilogram

Three equal masses are shown in the diagram. What is the direction of the net force acting upon m2?

leftwards

The physical quantity that is the measure of inertia is the

mass

Kinetic energy is energy that an object possesses because of its

motion

Suppose that the speed of a ball moving in a horizontal circle is increasing at a steady rate. Is this increase in speed produced by the centripetal acceleration?

no

A ball hangs from a string attached to the ceiling, as shown in the diagram. What is the direction of the net force acting on the ball?

none, the net force equals zero

The force of the floor pushing up on you to counter your weight is an example of a ________ force.

normal

A synchronous satellite is one that does not move relative to the surface of the Earth; it is always above the same location. Why does such a satellite not just fall down to the Earth?

the net force on the satellite keep changing the direction is is going

What are the possible states of motion for the object pictured in the diagram, given the fact that the two forces acting on it are equal and opposite in direction?

the object can be moving at a constant velocity or be at rest

Two equal magnitude forces act on a box as shown in the diagram.

the object is not accelerating in the horizontal direction

A ball tied to a string fastened at the other end to a rigid support forms a pendulum.

the speed and velocity are changing

A truck and a bicycle are moving side by side with the same velocity. Which, if either, will require the larger impulse to bring it to a halt?

the truck

Two balls of the same mass are accelerated by different net forces such that the red ball gains a velocity twice that of the blue ball in the process. How does the work done by the net force acting on the red ball compare to the net force acting on the blue ball?

the work done by the force on the red ball was four times that done on the blue ball

A boy pushes his friend across a skating rink. Since the frictional forces are very small, the force exerted by the boy on his friend's back is the only significant force acting on the friend in the horizontal direction. How does the change in the kinetic energy of the friend compare with the work done by the force exerted by the boy?

the work done is equal to the kinetic energy increase

Which, if either, exerts the larger gravitational force on the other?

they both exert the same force on each other

A compact car and a large truck have a head-on collision. During the collisions, which vehicle, if either, experiences: the greatest impulse?

they both experience the same

If an airbag inflates too rapidly and firmly during a collision it can sometimes do more harm than good in low-velocity collisions.

true

A fullback collides midair and head-on with a lighter defensive back. If the two players move together following the collision, is it possible that the fullback will be carried backward?

yes

What are the units for the constant G used in Newton's law of universal gravitation?

(N m2)/kg2

The velocity of a car traveling in the positive direction decreases from 38 m/s to 30 m/s in 4.5 seconds. What is the average acceleration of the car in this process?

-1.78 m/s2

If you are traveling 80 mph, how many hours does it take you to go 80 miles?

1

For a 0.1-kg frog to jump to a height of 1.0 meter requires an energy of about

1.0 Joule

A single force of 55 N acts upon a 32-kg block. What is the magnitude of the acceleration of the block?

1.72m/s2

A 30-kg child runs at 3.0 m/s and jumps onto a shopping cart and holds on for dear life. The cart has a mass of 20 kg. Assuming the child rides on the cart after the collision, the speed of the child and shopping cart just after the child jumps on is

1.8m/s

A box is moved 20 m across a smooth floor by a force making a downward angle with the floor, so that there is effectively a 10 N force acting parallel to the floor in the direction of motion and a 5 N force acting perpendicular to the floor. The work done is

200 Joule

A heavy ball with a mass of 4.5 kg is observed to accelerate at a rate of 7 m/s2. What is the magnitude of the net force acting on this ball?

31.5 N

A car is decelerating at the rate of 2 km/s2. If its initial speed is 66 km/s, how long will it take the car to come to a complete stop?

33s

A coil spring in an off-road truck with a spring constant k of 87.6 kN/m (87,600 N/m) is compressed a distance of 9.2 cm (0.092 m) from its original unstretched position. What is the increase in potential energy of the spring?

370.72 J

If the speed of a car is doubled but the brakes apply the same force, the distance required to stop the car changes by a factor of

4

What is the weight of a 45-kg mass? Use g = 9.81 m/s2.

441.45 N

A net force of 30 N acting on a wooden block produces an acceleration of 6 m/s2 for the block. What is the mass of the block?

5 kg

A walker covers a distance of 3 km in a time of 36 minutes. What is the average speed of the walker for this distance in km/h?

5 km/h

A car travels a distance of 100 km. For the first 30 minutes it is driven at a constant speed of 80 km/hr. The motor begins to vibrate and the driver reduces the speed to 40 km/hr for the rest of the trip. The average speed for the entire trip is

50 km/hr

In order to go from rest to 50 m/s in 10 s, a jet must be able to accelerate at

5m/s2

A car travels with an average speed of 38 MPH. What is this speed in km/h?

61.15 km/h

Your mass is 50 kg. Suppose you are standing on a scale in an elevator that starts moving up and increases its speed at the rate of 3 m/s every second. What would be the reading on the scale?

640 N

What is the mass of a 760-N weight? Use g = 9.81 m/s2. (Round the final answer to four decimal places.)

77.472kg

Object A moving due east collides with object B moving due west. After the collision, A is moving 20° north of due east. What must be true of B after the collision?

At least part of B's velocity must be toward the south

You have three carts connected by strings, as shown in diagram. Assume their masses are such that M1 > M2 > M3 . If a force, F, is applied to M1 and the net force on M2 is called F2 and the net force on M3 is called F3 , which of the following correctly states the relative size of each force?

F > F2 > F3

A light body and a heavy body are both given identical accelerations. The body acted upon by the larger force is the ________________ body.

Heavy

The following quantities relate to the rate of change of position. Which pair will always have the same magnitude?

Instantaneous speed and instantaneous velocity

An object undergoes uniform circular motion. Which pair of vectors is perpendicular?

Its centripetal acceleration and velocity vectors

The fundamental unit of work and energy is the

Joule

A shiny, spherical, metal alien jumps out of a perfectly good airplane and skydives for a few seconds. Its photographic friend snaps photos of the sphere with a special camera that also captures the forces on the object. This diagram shows a few of the snapshots, but they are out of order. Place them in order, from the instant it jumps out of the plane and begins free-fall until the time it attains terminal velocity. Assume that the parachute has not deployed yet. If any of the diagrams depict a situation not physically possible, omit it from the ordering.

L,J,Q

Is mass a force?

No

Is the elastic potential energy stored in the pole of a pole vaulter the only the only type of potential energy involved in pole-vaulting?

No

Suppose that the acceleration of a car increases with time. Could we use the relationship v = v_0 + at in this situation?

No

The instantaneous velocity of a toy car traveling in a straight line is shown in the graph. At which of the following times is the car accelerating?

T= 20, 30, 50 s

The gravitational force acting on a lead ball is much larger than that acting on a wooden ball of the same size. Which statement is true about when they are dropped?

The acceleration due to gravity is the same for both balls.

Two artificial satellites are in circular orbits about the Earth. Which of the two will be moving more slowly along its orbit?

The higher one

Consider two blocks, one made of wood and the other of lead. They have the same dimensions but the lead is much more massive. If they are dropped and fall long enough to reach terminal velocity, which block experiences a larger force from air resistance?

The lead block

A tennis ball bounces off a brick wall. Which of the following is true?

The total momentum of the ball, wall, and Earth is conserved in this process

A woman weighs 174 lb and another woman weighs 718 N. The woman weighing 174 lb has the greater mass.

True

Virgil rides a skateboard (combined mass 100 kg) at 4 m/s, and Jill rides a bicycle (combined mass 64 kg) at 5 m/s.

Virgil and Jill have equal kinetic energies.

For a uniformly accelerated car, is the average acceleration equal to the instantaneous acceleration?

Yes

In attempting to pull a 1500-kg car out of a ditch, Arnold exerts a force of 300 N for three seconds, Bob exerts a force of 500 N for two seconds, and Cecil exerts a force of 200 N for four seconds. Who provided the greatest impulse?

bob

A compact car and a large truck have a head-on collision. During the collisions, which vehicle, if either, experiences: the greater change in momentum?

both experience the same change in momentum

Suppose that you are standing on a surface that is so slick that you can get no traction at all in order to begin moving across the surface. Fortunately you are carrying a bag of oranges. How can you get yourself moving to the right?

by throwing the oranges to the left

A painter of mass 80 kg climbs 3.0 m up a ladder. The painter has gained momentum in the amount of

can't solve without velocity change

A box is moved 10 m across a smooth floor by a force F making a downward angle with the floor, so that there is effectively a 4 N force acting parallel to the floor in the direction of motion and a 3 N force acting perpendicular to the floor. The force F acts for 20 seconds. The impulse delivered to the box by the floor during this process has magnitude

can't solve without weight

The frictional force, due to air resistance, acting on an object is always

in the opposite direction to the object's motion.

How does an increased length of time that a force acts on an object affect the strength of the impulse produced?

increases

Suppose that on a perfectly still day, a sailboat enthusiast decides to bring along a powerful battery-operated fan in order to provide an air current for his sail, as shown in the diagram. What are the directions of the forces acting on the fan and on the sail due to these changes in momentum?

on the fan: to the left, on the sail: to the right

A moving cue ball strikes another ball of equal mass that is initially at rest on the flat planar surface of the pool table. If the collision is elastic, the direction of the velocity of the cue ball after the collision will be __________________ to the direction of the velocity of the other ball.

perpendicular

If the output piston in a hydraulic pump exerts a greater force than one applied to the input piston, how is the pressure at the output piston compared with the input piston?

same

Which of the following quantities relating to motion is not a vector?

speed

A penny and a quarter are embedded in the concrete bottom of a swimming pool filled with water. Which, if either, of these coins experiences the greater downward force due to water pressure?

the quarter

The fluid in a hydraulic system pushes against two pistons, one with a large area and the other with a small area. When the smaller piston moves, how does it compare to the larger piston?

the smaller piston moves more than the larger piston

Consider a system containing three objects that move with different velocities. The objects can interact with each other through forces. In this system

the total momentum of the objects cannot change unless an outside force acts on the system.

Is it possible for a rocket to function in empty space (in a vacuum) where there is nothing to push against itself?

yes, by ejecting exhaust

A ball is being twirled in a circle at the end of a string. The string provides the centripetal force needed to keep the ball moving in a circle at constant speed. What is the sign of the work done by the string on the ball in this situation?

zero, the string does no work

When you lift a heavy 5.0 kg crate straight up from ground level to a height of 2.0 m above ground level, then you have changed the crate's gravitational potential energy by

98J

A car rounds a curve while maintaining constant speed. Which of the statements is correct?

A net force acts upon the car

A hockey puck is sliding on frictionless ice. It slams against a wall and bounces towards the player. In which of the following cases has the puck's velocity changed?

All of these choices are correct.

Aristotle believed that a force was necessary to keep an object moving. Where, in his view, did this force come from in the case of a ball moving through the air?

Aristotle believed that the air rushed around the ball to fill the void of where it had been and this air pushed the ball forward.