Physics 2001: Midterm PLV questions (online)

A projectile is launched in the air and follows the parabolic path shown. When it reaches the peak in its trajectory, what is the acceleration of the projectile?

-g m/s2

A pushing force of 10 000 N is applied to the backside of a car at an angle of 25.0° above the horizontal, moving the car through a horizontal distance of 15.0 m. What is the work done by the force?

1.36 × 105 J

A pushing force of 10 000 N is applied to the backside of a car at an angle of 25.0° above the horizontal, moving the car through a horizontal distance of 15.0 m. If the car has a mass of 2 250 kg, what is its final speed?

11.0 m/s

A displacement vector R has a magnitude of 175 m directed at an angle of 50° north of east. What is the x-component of this displacement vector?

112 m due east

A powerboat, starting from rest maintains a constant acceleration. After a certain time t , its displacement and velocity are R and V . At time 2T, what will be its displacement and velocity, assuming the acceleration remains constant?

4 R and 2 V

Consider the same right triangle from the previous question. Find the value of the angle .

40 degree

A car is traveling in uniform circular motion on a section of flat roadway whose radius is r. The road is slippery, and the car is just on the verge of sliding off the roadway. If the car's speed were now doubled, what would be the smallest radius of the curve it could drive on without slipping?

4r

A 90.0-kg man runs at a constant speed of 11.5 m/s. What is his kinetic energy?

5 950 J

Consider the value 0.000574 m. Which of the following choices correctly represents this quantity written in scientific notation?

5.74 X 10-4 m

Imagine you are confined to the floor of gymnasium that is 100 meters long and 75 meters wide. Starting at any one of the corners, what is your maximum possible displacement?

75 meters

Which of the following does NOT represent an inertial frame of reference? A car going around a circular track at a constant speed. A skydiver falling straight downward at a constant (terminal) speed. A boat moving at a constant speed along a straight path. An airplane in straight and level flight at a constant speed.

A car going around a circular track at a constant speed.

The following figure shows the displacement vector of a car. Which of the following is the correct description of this vector?

A distance of 10 km in a direction of 30° north of west

In Case A, an object is moving in a straight line at a constant speed of 9.8 m/s. In Case B, an object is moving in a straight line with a constant acceleration of 9.8 m/s2. Which of the following statements is true? A nonzero net external force acts on the object in Case B only. A nonzero net external force acts on the object in neither case. A nonzero net external force acts on the object in both cases. A nonzero net external force acts on the object in Case A only.

A nonzero net external force acts on the object in Case B only.

Which of the following is not a system of units used in measurements? -SI (System International) -CGS (Centimeter, Gram, Second) -BE (British Engineering) -ATT (Angles, Temperature, Time) -None of these is a system of units.

ATT (angles, temperature, time)

A box is at rest on the floor of an elevator. Because of static friction, a force is required to start the box sliding across the elevator floor. Compare the size of the pushing force required to move the box, when the elevator is (a) stationary, (b) accelerating upward, and (c) accelerating downward. Rank these forces from smallest to largest.

Accelerating downward, stationary, accelerating upward

Which of the following describe nonequilibrium conditions in the context applying Newton's laws of motion? A spacecraft decelerating upon reentry into the atmosphere. A car accelerating through a traffic light. A ball falling off the roof of a house. A roller coaster going over the crest of a hill. All of the above.

All of the above.

Which of the following statements about centripetal acceleration is true? I. An object moving with a constant velocity cannot have a centripetal acceleration. II. An object moving with a constant speed may have a centripetal acceleration.

Both I and II

A body is moved from sea level to the top of a high mountain. Which of the following statements is/are true concerning the following quantities?I. The body's mass. II. The body's weight III. The gravitational force on the body.

Both II and III change

The vectors in the figure satisfy the following relationship A+B=C, where the magnitude of both vector A and B is equal to 175 m. Given the other information shown in the figure, what are the magnitudes of the x- and y-components of vector C.

Cx= 189m Cy= 246m

Note that all of the kinematic equations contain the initial velocity, v0. If a problem gives you three kinematic variables that does not include v0 , and you are asked to find a variable other than v0, how should you proceed?

First, use the three given variables to obtain v0, and then use a second equation to find the unknown variable asked for in the problem.

An object is undergoing uniform circular motion. Which of the following changes would increase the period of the motion? I. Increase the radius of the circular motion. II. Decrease the radius of the circular motion. III. Increase the speed of the object. IV. Decrease the speed of the object.

I and IV

A father and his seven-year-old daughter are facing each other on ice skates. With their hands, they push off against one another. Which of the following statements is/are true? I. Each experiences an acceleration that has a different magnitude. II. Each experiences an acceleration that has the same magnitude. III. Each experiences a pushing force that has a different magnitude. IV. Each experiences a pushing force that has the same magnitude.

I and IV only

Which of the following is/are true? I. The centripetal force points in toward the center of the circular motion. II. The centripetal force is independent of the object's mass. III. The centripetal force points in the opposite direction as the centripetal acceleration. IV. The centripetal force is a new and separate force created by nature, and therefore should appear in a free-body diagram.

I only

An object is undergoing uniform circular motion. Which of the following is/are true? I. The object is moving at constant velocity. II. The object is moving at constant speed. III. The object is accelerating.

II and III

Which of the following is/are true? I. Force is a scalar quantity. II. Force is a vector quantity. III. A force is a push or a pull between objects that occurs only when the objects are in physical contact. IV. Non-contact forces are also called action-at-a-distance forces.

II and IV only

Which of the following is/are true? I. Mass is a vector quantity. II. Mass is a scalar quantity. III. Mass is a measure of how much matter an object contains. IV. There is no relationship between force and mass. V. Isaac Newton developed three important laws of motion that describe the relationship between force and mass.

II, III, and V only

A new car leaves a parking lot with its odometer indicating 23 miles. Two hours later it returns with an odometer reading of 123 miles. Which statement is true of the car's trip? -Its average speed was zero, its displacement was zero, and its average velocity was 50 m.p.h. -Its average speed was 50 m.p.h, its displacement was 100 miles, and its average velocity was zero. -Its average speed was 50 m.p.h, its displacement was zero, and its average velocity was zero. -Its average speed was zero, its displacement was 100 miles, and its average velocity was 50 m.p.h.

Its average speed was 50 m.p.h, its displacement was zero, and its average velocity was zero.

A car undergoes a constant deceleration (the acceleration is opposite to its velocity). Which statement is true of the car assuming a truly constant (negative) acceleration?

Its velocity will eventually pass through zero, reverse direction, and continue to accelerate in the opposite direction.

Three boys of equal strength try to break a rope (and fail) by tying one end to a fence post and tugging on the other end. Three additional boys (about the same strength as the others) come along and offer their assistance. Which of the following will maximize the tension in the rope? Untie the rope from the post and have three boys tug on one end and the remaining three on the other (like a tug-of-war). It does not matter: the rope sustains the same tension in both cases. Keep one end of the rope tied to the post and have all six boys tug on the other end.

Keep one end of the rope tied to the post and have all six boys tug on the other end.

Which of the following statements is true? Newton's third law is also known as F=m⁢a. Newton's third law is only valid for contact forces. Newton's third law states that for every acceleration of one object, there is an equal but opposite acceleration of another object. Newton's third law is also known as the action/reaction law.

Newton's third law is also known as the action/reaction law.

Consider a velocity-time graph that consists of a curve rather than a line of constant slope. Can you use the equations of kinematics to describe the motion of an object undergoing motion described by such a graph?

No. The curve represents a non-constant acceleration, and the kinematic equations were derived assuming a constant acceleration.

Which of the following statements is correct concerning satellites in orbit around the same planet? The period of a satellite depends on its mass. Satellites located closer to the planet have longer periods. The period of a satellite is independent of the planet's mass. If the orbital radius of a satellite doubles, then its period increases by a factor of 4. None of the above statements are correct.

None of the above statements are correct.

Three particles have identical masses. Each particle experiences only the gravitational forces from the other two particles. How should the particles be arranged so that each one experiences a net gravitational force of the same magnitude? On three of the four corners of a square. Equally spaced on a straight line. On the corners of an equilateral triangle. On the corners of a right triangle.

On the corners of an equilateral triangle.

To attain its takeoff speed, the typical land-based takeoff distance for a certain fighter jet is 500 m. On an aircraft carrier, that same jet must takeoff at a reduced distance of 100 m, so the jet gets "assisted" by a steam-driven catapult. Assuming a constant acceleration in both cases, how does the magnitude of the acceleration of the jet when taking off from the carrier compare to its acceleration when it takes off from the land-based runway?

The acceleration for the aircraft carrier launch is 5 times that of the land-based takeoff.

You and a friend are standing on the edge of a cliff of height h. You throw a ball straight upward at the same time your friend throws a ball straight downward, off the edge. You both throw with the same initial speed,v0 . Assuming the ball projected upward misses the edge of the cliff on the way down, which ball will hit the ground first, and which one will hit with the greater velocity?

The ball project downward will hit first, but the two will hit with equal velocities.

Considering that there are only three fundamental forces in nature from which all other forces can be derived, which of the three are responsible for the forces between atoms that hold solid materials together? It is the gravitational attraction (the gravitational force) between the atoms. The electroweak force because the bonding in materials is carried out by electrons (electric charges). It is the nuclear strong force between the nucleons in the nuclei of the atoms.

The electroweak force because the bonding in materials is carried out by electrons (electric charges).

A square, four-legged table with a weight of 400 N rests on an even concrete floor. Assuming the weight is evenly distributed, what is the direction and magnitude of the normal force between the floor and each foot of the table? The floor provides a normal force vertically upward (perpendicular to the floor) on each leg with a magnitude of 100 N. The floor provides a force vertically upward (perpendicular to the floor) on each leg with a magnitude of 400 N. The floor provides a normal force parallel to the floor on each leg with a magnitude of 100 N. The floor provides a force parallel to the floor on each leg with a magnitude of 400 N.

The floor provides a normal force vertically upward (perpendicular to the floor) on each leg with a magnitude of 100 N.

A deer runs north 500 m, then turns south and runs 750 m. Which statement is true? -The magnitude of the displacement is less than the total distance traveled, and the resultant displacement vector points south. -The magnitude of the displacement is zero. -The magnitude of the displacement is equal to the total distance traveled, and the resultant displacement vector points south. -The magnitude of the displacement is equal to the total distance traveled, and the resultant displacement vector points north.

The magnitude of the displacement is less than the total distance traveled, and the resultant displacement vector points south.

Suppose the coefficients of static and kinetic friction have values such that μs=1.4μk for a crate in contact with a cement floor. Which of the following statements is true? The magnitude of the kinetic friction force on the crate is always 1.4 times as large as the static friction force. The magnitude of the maximum static friction force on the crate is 1.4 times as large as the kinetic friction force. The magnitude of the static friction force on the crate is always 1.4 times as large as the kinetic friction force.

The magnitude of the maximum static friction force on the crate is 1.4 times as large as the kinetic friction force.

In which location does a 15-kg bowling ball have the smallest mass? On the moon where the force due to gravity is less than on earth. In deep space where there is no force due to gravity. The mass is the same everywhere. On Earth.

The mass is the same everywhere.

The net external force acting on an object is zero. Which of the following statements is/are true? The object can only be traveling with a velocity that is changing. The object can be either stationary or traveling with constant velocity. The object can only be stationary. The object can only be traveling with a constant velocity.

The object can be either stationary or traveling with constant velocity.

Consider two people on the surface of the earth. One is on the equator, and the other is at the North Pole. Which person experiences the larger centripetal acceleration? The person at the North Pole. Both experience the same centripetal acceleration. The person at the equator.

The person at the equator

Consider two identical frictionless and banked curves - one is located on the earth, and the other is on the moon. If identical cars are to travel around each curve along a circle of the same radius, how must the speeds of the two cars compare? The speeds of the two cars must be the same. The speed of the car on the moon must be greater than the speed of the car on the earth. The speed of the car on the earth must be greater than the speed of the car on the moon.

The speed of the car on the earth must be greater than the speed of the car on the moon.

A satellite is in a circular orbit around a planet. A second satellite is placed in a different circular orbit that is farther away from the same planet. How do the speeds of the two satellites compare? The speed of the second satellite is less than the speed of the first satellite. The speed of the second satellite is greater than the speed of the first satellite. The speeds of the two satellites are equal.

The speed of the second satellite is less than the speed of the first satellite.

A rotating space station creates artificial earth-like gravity. If the size of the space station is enlarged, such that its radius increases by a factor of 4, what must happen to the speed of the station floor, so that the artificial earth-like gravity is maintained?

The speed of the station floor should increase by a factor of 2.

A stone is thrown from the top of a high cliff. Air resistance is negligible. As the stone falls, which of the following is true? The stone is never in equilibrium as it falls. The stone is in equilibrium continuously as it falls. The stone is in equilibrium during the first half of its fall and then nonequilibrium for the second half.

The stone is never in equilibrium as it falls.

Which statement is true regarding a jet moving at a constant speed of 450 m.p.h. in straight and level flight. There is a net force acting on the jet, but only in the upward direction - otherwise it could not maintain flight. With no net force, the jet would eventually slow down. There is no net force acting on the jet. With no net force, the jet would lose altitude.

There is no net force acting on the jet.

In which one of the following situations could an object possibly be in equilibrium? Three forces act on a single object. The forces all point along the same line, but may have different directions. Two perpendicular forces act on an object. A single force acts on an object. None of the above.

Three forces act on a single object. The forces all point along the same line, but may have different directions.

A stone is tied to a string and swung along the path of a vertical circle at constant speed. When is the string most likely to break?

When the stone is at the very bottom of the circle.

Of the four kinematic equations, is it possible to get two possible solutions from the same equation? If so, which ones?

Yes. Whenever one of the variables is squared, that equation may provide two possible solutions. There are two such equations: x= v0t + 1/2at2 and v2=v02 + 2ax

You are in a car that is traveling at constant speed on a straight and level road before it suddenly starts down a hill. What can be said of your apparent weight relative to your true weight just as the car starts down the hill? Your apparent weight is equal to your true weight. Your apparent weight is less than your true weight. Your apparent weight is greater than your true weight.

Your apparent weight is less than your true weight.

You are standing on a scale and in a fast elevator that is taking you to the top of a tall building. The elevator slows as it reaches the top. What is true of your apparent weight as the elevator decelerates? Your apparent weight is less than your true weight. Your apparent weight is equal to your true weight. Your apparent weight is greater than your true weight.

Your apparent weight is less than your true weight.

Which of the following is an example of a vector quantity? -A temperature of +20 °C -A car's speedometer and compass reading of 65 mi/h due east -An object's mass of 34 kg -A time of 7.9 s -A car's speedometer reading of 65 mi/h

a car's speedometer and compass reading of 65 mi/h due east

Which of the following statements is/are true? -Physics is the most fundamental of all the branches of science. -Physics is a very mature science, where its fundamental principles have been tested over many centuries and supported by empirical evidence from experimentation. -Physics provides a framework for explaining the processes of the natural world. -Physics research has had a significant impact on the development of new technologies, such as space travel, telecommunications, and medicine. -All of the above statements are true.

all of the above

Two cars are identical except for the tread design on their tires. They both enter an unbanked horizontal curve at the same speed. Car A cannot negotiate the turn (it slides off), but Car B can. Which tread design, the one on Car A, or the one on Car B, yields the larger coefficient of static friction between the tires and the road?

car B

A stone is thrown horizontally from the top of a cliff and eventually hits the ground below. A second stone is dropped from rest from the same cliff, falls through the same height, and also hits the ground below. Consider the three quantities below. Are they the same for the two stones, or different? a.) displacement b.) speed just before impact with the ground c) time of flight

different different same

An apple tree is being moved on the back of a flatbed truck at constant speed from left to right, when an observer on the truck sees an apple fall from the tree and fall straight down. What path would an observer at rest on the ground see the falling apple follow?

down to the right

True or False: It is ok to add different units together, as long as they have the same dimensions. For example, while 25 mi and 12 km have different units, we can add them together (without conversion) since they both have the dimension of length.

false

True or False? When an astronaut is in orbit around the earth, she is weightless?

false

Can two nonzero perpendicular vectors be added together so their sum is equal to zero?

no

Consider the vector equation A + B = C. The component method of vector addition specifies that the scalar components of the resultant vector C are given by Cx=Ax+Bx and Cy=Ay+By Which of the following would give the magnitude of the resultant vector C?

square root: Cx2 + Cy2

Three swimmers can swim equally fast relative to the water. They have a race to see who can swim across a flowing river in the least time. Swimmer A swims perpendicular to the current and lands on the opposite shore downstream, because the current has swept him in that direction. Swimmer B swims upstream at angle to the current, so that when she reaches the other side, she is straight across from where she started. Swimmer C swims downstream at an angle theta in an attempt to take advantage of the current. Who crosses the river in the least time?

swimmer A

Suppose you drive 1500 m due east in 2 minutes. You then turn due north and drive the same distance in the same time. Which of the following is true concerning the average speeds and average velocities for each segment of your trip?

the average speeds are the same, but the average velocities are different

Which of the following is true concerning the relationship between the total distance an object moves and the displacement of the object?

the displacement will be less than or equal to the total distance

The phrase "it starts from rest" appears in statement of a kinematics problem regarding the motion of an object. What can you infer from this statement?

the initial velocity of the object is zero

Consider a position-time graph that consists of a single line segment of positive slope. Which one of the following is true?

the velocity is positive, but the acceleration is zero

A rock is thrown vertically. What is true when the rock reaches its maximum height?

the velocity is zero, and the acceleration is -g

At t=0 , an object is moving with constant velocity in the xy- plane, where its velocity vector makes an angle of 45° relative to the positive x axis. The object then accelerates for 2 seconds in the positive ydirection only. After the 2 seconds, which of the following is true?

the velocity vector of the object is directed at an angle greater than 45 degree above the positive x axis

True or False: If the magnitudes of both the x- and y-component of a vector are doubled, then the magnitude of the vector is also doubled.

true

Vectors A, B, andC and satisfy the following equation A + B = C, and their magnitudes are related by the scalar equation A + B = C . How is vector A oriented with respect to vector B?

vectors A and B are collinear and point in the same direction

A kinematics problem asks for the value of the acceleration and provides values for , , and the initial velocity. Which equation should you use?

x= V0t + 1/2at2

To answer this question, first click here to view the associated video. Below is a list of variables and their corresponding units. Variable Units x Meters (m) v Meters per second (m/s) t Seconds (s) a Meters per second squared (m/s2) Consider the following relationship: . Is this relationship t= square rt 2x/a dimensionally consistent? In other words, do the units on the left side of the equation match the units on the right side?

yes

A cop gets a call indicating that a red sports car passed mile marker 3 on a highway with a speed limit of 60 m.p.h. Exactly five minutes later the car passes the cop, who is sitting at mile marker number 9. Even though the cop's radar indicates that the car is going the speed limit, was the car speeding at any point between markers 3 and 9?

yes, the car's average speed was 72 mph

Consider the right triangle shown in the figure. The two angles and are not given, but we know the length of the two shorter sides (legs). Can you calculate the length of the longest side (hypotenuse, )? If so, what is its length?

yes. h-39

You and your friends are riding a rollercoaster. You enter a vertical loop-the-loop, turn upside-down, and then come out again at the bottom of the loop. This is similar to what the motorcycle stuntman did in the video. As you pass through the very bottom of the loop, do you feel heavier or lighter than normal?

you feel heavier

A cable applies a vertical force to a crate with a mass of 70.0 kg. It first lifts the crate to a height of 12.0 m above the floor, and then lowers it back to the floor. What is the total work done by the force?

zero