Physics: Chapter 1, 2, 3, and 7 Concept Questions
In one-dimensional motion, the average speed of an object that moves from one place to another and then back to its original place has which of the following properties?
It is positive
A car is going around a racetrack at constant speed. The curves around the track have different radii. In which turn is the magnitude of the car's acceleration the greatest?
It is the greatest in the turn with the smallest radius.
Consider the sine of any angle between 30 and 40 . If the angle were doubled, what would happen to the sine of the angle?
It would increase but be less than double.
Suppose an equation relating position, x, to time, t, is given by x = b t3 + c t4, where b and c are constants. The dimensions of b and c are respectively:
L/T^3, L/T^4.
Areas always have dimensions ____ while volumes always have dimensions ____.
L^2, L^3
Somewhere between the Earth and the Moon is a point where the gravitational attraction of the Earth is canceled by the gravitational pull of the Moon. The mass of the Moon is 1/81 that of the Earth. How far from the center of the Earth is this point?
9/10 the way to the Moon
A ball rolls down an incline, starting from rest. If the total time it takes to reach the end of the incline is T, how much time has elapsed when it is halfway down the incline?
> 0.5 T
Which of the following best describes the property of the period of orbital revolution for an Earth satellite?
greater when the orbital radius is larger
Of the nine known planets in our solar system, the innermost is Mercury. When compared to the other planets in the system, Mercury has the:
greatest centripetal acceleration.
In the case of constant acceleration, the average velocity equals the instantaneous velocity:
half-way through the time interval.
When was the existence of the neutron confirmed?
in 1932
A wheel is rotated about a horizontal axle at a constant angular speed. Next it is rotated in the opposite direction with the same angular speed. The acceleration at a point on the top of the wheel in the second case as compared to the acceleration in the first case:
is in the same direction.
In mechanics, physicists use three basic quantities to derive additional quantities. Mass is one of the three quantities. What are the other two?
length and time
The speed of a boat is often given in knots. If a speed of 5 knots were expressed in the SI system of units, the units would be:
m/s.
A plane is moving due north, directly towards its destination. Its airspeed is 200 mph. A constant breeze is blowing from west to east at 40 mph. How long will it take for the plane to travel 200 miles north?
more than one hour
An artificial Earth satellite in an elliptical orbit has its greatest centripetal acceleration when it is at what location?
nearest the Earth
At what location does an artificial Earth satellite in elliptical orbit have its greatest speed?
nearest the Earth
Consider a child who is swinging. As she reaches the lowest point in her swing:
none of the above.
At an altitude of 4 times the radius of the earth, the acceleration due to gravity is
not given.
According to Kepler's second law, Halley's Comet circles the Sun in an elliptical path with the Sun at one focus of the ellipse. What is at the other focus of the ellipse?
nothing
A runner circles a track of radius 100 m one time in 100 s at a constant rate. The greatest change in his velocity from his starting velocity:
occurs one-half of the way around the track.
If the displacement of an object is given in SI units by Dx = -3 t + 4 t 2, at t = 2 s its velocity and acceleration are, respectively:
positive, positive
The nuclei of atoms contain
protons and neutrons.
The value of an object's acceleration may be characterized in equivalent words by which of the following?
rate of change of velocity
Changing the positive direction in a reference frame to the opposite direction does not change the sign of which of the following quantities?
speed
A strobe photograph shows equally spaced images of a car moving along a straight road. If the time intervals between images is constant, which of the following cannot be positive?
the acceleration of the car
A strobe photograph of a car moving along a straight road shows the interval between each successive image to be diminishing. If the direction of motion of the car is taken as positive, which of the following are negative?
the average acceleration of the car
An x vs. t graph is drawn for a ball moving in one direction. The graph starts at the origin and at t = 5 s the velocity of the ball is zero. We can be positive that at t = 5 s,
the ball has stopped.
Since 1983 the standard meter has been defined in terms of which of the following?
the distance light travels in a certain fraction of a second
A projectile is launched at an angle q above the horizontal. Three seconds later the projectile is moving the same angle q below the horizontal.Which of the following (actual values with units, not just algebraic symbols) can be found from the information given?
the initial vertical component of the projectile's velocity
A boat moves through the water in a river at a speed of 8 m/s relative to the water. The boat makes a trip downstream and then makes a return trip upstream to the original starting place. Which trip takes longer?
the upstream trip
A v vs. t graph is drawn for a ball moving in one direction. The graph starts at the origin and at t = 5 s the acceleration of the ball is zero. We know that at t = 5 s,
the velocity of the ball is not changing
If the displacement of an object, x, is related to velocity, v, according to the relation x = Av, the constant, A, has the dimension of which of the following?
time
You are facing east looking at the clock on the wall. You see the second hand moving clockwise (of course). In what direction is the angular velocity vector for this second hand?
east
The prefixes which are abbreviated p, n, and G represent which of the following?
10^-12, 10^-9, and 10^9
Which of the following is not a vector quantity?
temperature
The slope of the acceleration vs. time curve represents:
the rate of change of acceleration.
The proton contains which of the following combination of quarks?
two up quarks and one down quark
Consider a point on a bicycle tire that is momentarily in contact with the ground as the bicycle rolls across the ground with constant speed. The direction for the acceleration for this point at that moment is
upward.
If a is acceleration, v is velocity, x is position, and t is time, then which equation is not dimensionally correct?
v = a/t
Which expression is dimensionally consistent with an expression that would yield a value for time-1? (v is velocity, x is distance, and t is time)
v/x
Displacement is which of the following types of quantities?
vector
Which type of quantity is characterized by both magnitude and direction?
vector
Which of the following is an example of a vector quantity?
velocity
Two satellites are monitored as they orbit the Earth; satellite X is eight times as far from the Earth's center as is satellite Y. From Kepler's third law one may conclude that the period or revolution of X is what factor times that of Y?
22.6
A runner circles a track of radius 100 m in 100 s moving at a constant rate. If the runner was initially moving north, what has been the runner's average acceleration when halfway around the track?
0.25 m/s2, south
If j = 90 - q, what is the value of sin2 j + sin2 q?
1
For any object orbiting the Sun, Kepler's Law may be written T2 = kr3. If T is measured in years and r in units of the Earth's distance from the Sun, then k = 1. What, therefore, is the time (in years) for Mars to orbit the Sun if its mean radius from the Sun is 1.5 times the Earth's distance from the Sun?
1.8 years
The ratio M/m of the prefixes M and m has what value?
10^9
In which of the following cases is the displacement's magnitude half the distance traveled?
15 steps east followed by 5 steps west
An asteroid in orbit about the sun has a linear speed of 4 km/s when at a distance of closest approach d from the sun. What is its linear speed when it is at its greatest distance from the sun, a distance 2 d?
2 km/s
Doubling the mean distance from the Sun results in changing the orbital period of revolution by what factor?
2^3/2
One year is about ____ seconds while one day is exactly ____ seconds.
3.16 x 10^7, 86,400
Doubling the radius of a sphere results in increasing its volume by a factor of
8
An asteroid is in orbit at 4 times the earth's distance from the Sun. What is its period of revolution?
8 years
For a point on a spinning disc in uniform circular motion, which of the following is not constant?
Its centripetal acceleration.
Two projectiles are launched at 100 m/s, the angle of elevation for the first being 30 and for the second 60 . Which of the following statements is false?
All of the above statements are false.
Two objects of different mass are released simultaneously from the top of a 20-m tower and fall to the ground. If air resistance is negligible, which statement best applies?
Both objects hit the ground together.
Note the expression: y = x2. Which statement is most consistent with this expression?
If x doubles, then y quadruples.
Note the expression: y = A/x3. Which statement is most consistent with this expression?
If x is halved, y is multiplied by eight.
In one-dimensional motion where the direction is indicated by a plus or minus sign, the average velocity of an object has which of the following properties?
It can be positive, negative, or zero.
A ball of relatively low density is thrown upwards. Because of air resistance the acceleration while traveling upwards is -10.8 m/s2. On its trip downward the resistance is in the opposite direction, and the resulting acceleration is -8.8 m/s2. When the ball reaches the level from which it was thrown, how does its speed compare to that with which it was thrown?
It is less than the original speed upward.
Two objects are in circular orbits of different radii around the Sun. Which object has the highest orbital speed?
The one closest to the Sun.
An object is dropped from a height. Once it is moving, which of the following statements is true, at least at one point?
Its velocity is never equal to its acceleration.
The Earth's orbit is closest to the Sun in January and farthest from the Sun in July. When is the Earth moving the fastest in orbit?
January
Consider a point on a bicycle wheel as the wheel turns about a fixed axis, neither speeding up nor slowing down. Compare the linear and angular accelerations of the point.
Only the angular acceleration is zero.
Consider a point on a bicycle wheel as the wheel turns about a fixed axis, neither speeding up nor slowing down. Compare the linear and angular velocities of the point.
Only the angular velocity is constant.
Consider a point on a bicycle wheel as the wheel makes exactly four complete revolutions about a fixed axis. Compare the linear and angular displacement of the point.
Only the linear displacement is zero.
A particle moves east at constant velocity for a time interval DT. It then moves north at a constant velocity, with the same speed as before, for another time interval DT. Finally it moves east again with the original velocity. At the instant an additional time interval DT has elapsed, which of the following are true about the average velocity and the average acceleration for the motion described?
The average velocity is not and the average acceleration is zero.
When SI units are plugged into an equation, it is found that the units balance. Which of the following can we expect to be true for this equation?
The equation will be dimensionally correct.
Starting from rest, a car accelerates down a straight road with constant acceleration a for a time t, then the direction of the acceleration is reversed, (i.e., it is -a), and the car comes to a stop in an additional time t, the time for the whole trip being 2t. At what time, or times, is the average velocity of the car for the trip equal to its instantaneous velocity during the trip?
This occurs at 2 times, 0.5 t and 1.5 t.
Starting from rest, a car accelerates down a straight road with constant acceleration a1 for a time t1, then the acceleration is changed to a different constant value a2 for an additional time t2. The total elapsed time is t1 + t2. Can the equations of kinematics be used to find the total distance traveled?
Yes, break the problem up into 2 problems, one with the conditions for the first time interval and the other with the conditions for the second time interval, noting that for the second time interval the initial velocity is that from the end of the first time interval. When done, add the distances from each of the time intervals.
How long has it been that scientists have accepted that the nucleus of the atom consists of neutrons and protons? Think of your answers in terms of order of magnitude.
about a century
A baseball is thrown by the center fielder (from shoulder level) to home plate where it is caught (on the fly at shoulder level) by the catcher. At what point is the magnitude of the acceleration at a minimum? (air resistance is negligible)
acceleration is constant during entire trajectory
When we add a displacement vector to another displacement vector, the result is:
another displacement.
When we subtract a velocity vector from another velocity vector, the result is:
another velocity.
Which formula is dimensionally consistent with an expression yielding a value for velocity? (a is acceleration, x is distance, and t is time)
at
Jeff throws a ball straight up. For which situation is the vertical velocity zero?
at the top
A baseball catcher throws a ball vertically upward and catches it in the same spot when it returns to his mitt. At what point in the ball's path does it experience zero velocity and non-zero acceleration at the same time?
at the top of its trajectory
A baseball is thrown by the center fielder (from shoulder level) to home plate where it is caught (on the fly at an equal shoulder level) by the catcher. At what point is the ball's speed at a minimum? (air resistance is negligible)
at the top of the trajectory
A baseball is thrown by the center fielder (from shoulder level) to home plate where it is caught (on the fly at shoulder level) by the catcher. At what point does the magnitude of the vertical component of velocity have its minimum value? (air resistance is negligible)
at the top of the trajectory
On a position versus time graph, the slope of the straight line joining two points on the plotted curve that are separated in time by the interval Dt, is which of the following quantities?
average velocity
In order for a satellite to be geosynchronous, its orbit must:
be over the equator.
Since 1967 the standard definition for the second has been based on which of the following?
characteristic frequency of the cesium-133 atom
In a 2-dimensional Cartesian coordinate system the x-component of a given vector is equal to that vector's magnitude multiplied by which trigonometric function, with respect to the angle between vector and xaxis?
cosine
In a 2-dimensional Cartesian coordinate system the y-component of a given vector is equal to that vector's magnitude multiplied by which trigonometric function, with respect to the angle between vector and yaxis?
cosine
In a 2-dimensional Cartesian system, the x-component of a vector is known, and the angle between vector and x-axis is known. Which operation is used to calculate the magnitude of the vector? (taken with respect to the x-component)
dividing by cosine
Two points on a merry-go-round are located at distances from the center r1 and r2, where r1 < r2. While the merry-go-round is in the process of speeding up to operational speed, which of the following equations involving magnitudes of angular speed, angular acceleration, and tangential speed for these points is incorrect?
vt1 = vt2
A change in a physical quantity w having initial value wi and final value wf is given by which of the following?
wf - wi