PLV questions
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 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
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?
125
What does NOT represent an inertial frame of reference?
A car going around a circular track at a constant speed.
Which of the following is not a system of units used in measurements?
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
True or False? When an astronaut is in orbit around the earth, she is weightless?
False
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 (centripetal acceleration) (not constant velocity bc going in different directions)
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? speed just before impact with the ground:
different
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?
downward sloping curve
A kinematics problem asks for the value of the acceleration and provides values for , , and the initial velocity. Which equation should you use?
x=v(initial)t + 1/2at^2
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/s^2
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
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.
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 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
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.
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.
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?
The electroweak force because the bonding in materials is carried out by electrons (electric charges).
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.
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 less than your true weight.
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
A car is traveling in uniform circular motion on a section of flat roadway whose radius is . 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 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?
4r and 4v
Consider the value 0.000574 m. Which of the following choices correctly represents this quantity written in scientific notation?
5.74 × 10-4 m
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 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 and if they are affected? I. The body's mass. II. The body's weight. III. The gravitational force on the body.
Both II and III change.
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
Note that all of the kinematic equations contain the initial velocity, . If a problem gives you three kinematic variables that do not including , and you are asked to find a variable other than , how should you proceed?
First, use the three given variables to obtain , 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
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-distanceforces.
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. Solve for average speed, displacement, and average velocity.
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?
Keep one end of the rope tied to the post and have all six boys tug on the other end.
What is true of newtons third law?
Newton's third law is also known as the action/reaction law.
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 the corners of an equilateral triangle.
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? time of flight:
Same
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
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
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.
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.
You and a friend are standing on the edge of a cliff of height . 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, . 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.
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 force parallel to the floor on each leg with a magnitude of 400 N.
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.
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.
Suppose the coefficients of static and kinetic friction have values such that for a crate in contact with a cement floor. Which of the following statements is true?
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?
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 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 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 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.
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
A rock is thrown vertically. What is true when the rock reaches its maximum height?
The velocity is zero, and the acceleration is
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 y-direction 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° above the positive x-axis.
Which statement is true regarding a jet moving at a constant speed of 450 m.p.h. in straight and level flight.
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.
Vectors AA,BB and CC satisfy the following equation A + B = CA + B = C, and their magnitudes are related by the scalar equation A + B=CA+B=C . How is vector AA oriented with respect to vector BB?
Vectors AA and BB are collinear and point in opposite 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.
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 m.p.h.
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: and
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.
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.
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? Displacement:
different
Can two nonzero perpendicular vectors be added together so their sum is equal to zero?
no