Physics final exam multiple choice
As shown in the figure, a given force is applied to a rod in several different ways. In which case is the torque about the pivot P due to this force the greatest?
1 the one with the force perpendicular to the rod at the very tip (as far away from the hinge as possible)
A 10-kg rock and a 20-kg rock are thrown upward with the same initial speed v0 and experience no significant air resistance. If the 10-kg rock reaches a maximum height h, what maximum height will the 20-kg ball reach
1*H
What is the expression for KE
1/2mv^2`
Vector F has an x-component of -10 N and a y-component of -4 N. The magnitude of F is:
10.8N
A car increases its forward velocity uniformly from 40 m/s to 80 m/s while traveling a distance of 200 m. What is its acceleration during this time?
12 m/s see first eqn
A 200-N sled of slides down a frictionless hillside that rises at 37° above the horizontal. What is the magnitude of the force that gravity exerts on the sled parallel to the surface of the hill
120N ( use eqn 6 to solve for N)
A 200-N sled of slides down a frictionless hillside that rises at 37° above the horizontal. What is the magnitude of the force that the surface of the hill exerts on the sled (the normal force)?
160N (use eqn 5)
The sum of two vectors of fixed magnitudes has its minimum magnitude when the angle between these vectors is
180 degrees
An ideal spring has a spring constant (force constant) of 2500 N/m. is stretched 4.0 cm. How much work is required to stretch the spring by 4.0 cm?
2.0 J use spring stretch eqn 10
Given a velocity, V = 5 m/s at 120 ∘. The x component (Vx) is:
2.5 m/s use cos!
Vector A = 10 m at 20∘. The vector - 2A is:
20 m at 200 degrees (multiply by 2 and add 180 degrees cause its the opposite.)
A girl throws a rock horizontally, with a velocity of 10 m/s, from a bridge. It falls 20 m to the water below. How far does the rock travel horizontally before striking the water, assuming negligible air resistance?
20 m use eqn 2
Vector F has an x-component of -10 N and a y-component of -4 N. The direction of F is:
202 degrees use arctan?
Consider a pipe of length L that is open at both ends. What are the wavelengths of the three lowest-pitch tones produced by this pipe?
2L, L, 2L/3
If electricity costs 7.06 cents/kWh, how much would it cost you to run a 120W stereo system 4 hours per day for 4 weeks (28 days)?
$0.95
A 1000.0 kg car experiences a net force of while decelerating from to How far does it travel while slowing down?
34 m use F=ma and solve for a for initial a. Then plug into eqn 1
A standing wave is oscillating at 950 Hz on a string, as shown in the figure. What is the wave speed with 60cm between posts?
380 m/s wave speed = lambda*frequency lambda = distance between posts*2/3
The number 0.003010 has
4 significant figures
Given a velocity, V = 5 m/s at 120 ∘. The y component (Vy) is:
4.33 m/s use sin!
A 50-kg box is being pushed along a horizontal surface. The coefficient of static friction between the box and the ground is 0.65, and the coefficient of kinetic friction is 0.35. What horizontal force must be exerted on the box for it to accelerate at 1.2 m/s2?
- 230 N (use eqn 3 to find force of friction then plug it into eqn 4 and solve for F)
The x component of vector A is 5.3 units and its y component is -2.3 units. The angle that vector A makes with the +x axis is closest to-
- 340 degrees
If a vector has components Ax < 0, and Ay > 0, then the angle that this vector makes with the positive x-axis must be in the range
- 90° to 180°
Two vectors, of magnitudes 20 mm and 50 mm, are added together. Which one of the following is a possible value for the magnitude of the resultant?
40mm
Vector = 4.00 m points eastward and vector = 3.00 m points southward. The resultant vector + is given by?
5.00 m at an angle of 36.9° south of east.
The position of an object that is oscillating on a spring is given by the equation x = (17.4 cm) cos[(5.46 s-1)t]. What is the angular frequency for this motion?
5.46 rad/s for the wave form eqn it goes A cos (w)(t) A=amplitude w=angular frequency t=time
A ball is thrown downward from the top of a building with an initial speed of 25 m/s. It strikes the ground after 2.0 s. How high is the building, assuming negligible air resistance
70 m
A child does 350 J of work while pulling a box from the ground up to his tree house with a rope. The tree house is above the ground. What is the mass of the box?
8.9 kg use PE energy eqn (11)
How much work would a child do while pulling a 12-kg wagon a distance of 4.3 m along a flat surface with a horizontal 22N force?
95J eqn for work is W=fd
Suppose that a car traveling to the west (-x direction) begins to slow down as it approaches a traffic light. Which statement concerning its acceleration must be correct?-
?- Its acceleration is positive.
Two children, Ahmed and Jacques, ride on a merry-go-round. Ahmed is at a greater distance from the axis of rotation than Jacques. Which of the following is a true statement?
Ahmed has a greater tangential speed than Jacques.
The magnitude of is 5.5 m, and this vector lies in the second quadrant and makes an angle of 34 ° with the +y-axis. The components of are closest to
Ax = -3.1 m, Ay = 4.6 m.
The figure shows scale drawings of four objects, each of the same mass and uniform thickness, with the mass distributed uniformly. Which one has the greatest moment of inertia when rotated about an axis perpendicular to the plane of the drawing at point P?
B (the bicycle wheel because almost all of the mass is located on the edge of the wheel.
Person X pushes twice as hard against a stationary brick wall as person Y. Which one of the following statements is correct?
Both do zero work.
A 4.0 kg object is moving with speed 2.0 m/s. A 1.0 kg object is moving with speed 4.0 m/s. Both objects encounter the same constant braking force, and are brought to rest. Which object travels the greater distance before stopping? (Hint: Use the Work-Energy Principle)
Both objects travel the same distance.
You and your friend, who weighs the same as you, want to go to the top of the Eiffel Tower. Your friend takes the elevator straight up. You decide to walk up the spiral stairway, taking longer to do so. Compare the gravitational potential energy of you and your friend, after you both reach the top.
Both of you have the same amount of gravitational potential energy at the top.
A 20-ton truck collides with a 1500-lb car. Which of the following statements must be true
During the collision, the force on the truck is equal to the force on the car.
If the sum of both the external forces and the external forces on an object is zero, then the object must be at rest T/F
False
If the sum of the external forces on an object is zero, then the sum of the external torques on it must also be zero. T/F
False
If the sum of the external torques on an object is zero, then the sum of the external forces on it must also be zero. T/F
False
If three vectors add to zero, they must all have equal magnitudes. T/F
False
T/F If a vector pointing upward has a positive magnitude, a vector pointing downward has a negative magnitude.
False
A spinning ice skater on extremely smooth ice is able to control the rate at which she rotates by pulling in her arms. Which of the following statements are true about the skater during this process?
Her angular momentum remains constant.
Three vectors S, T, and U, have the components shown in the table. What angle does the resultant of these three vectors make with the +x axis- add up all of the x and all of the y components separately and then use the resultant vector
. -66 degrees below the + x axis
What is to the proper number of significant figures?- .674/.74
.91
The sum of two vectors of fixed magnitudes has the greatest magnitude when the angle between these two vectors is
0 they are the greatest when on top of each other their values aren't averaged down
A ball is thrown downward in the absence of air resistance. After it has been released, which statement concerning its acceleration is correct
Its acceleration is constant
The acceleration due to gravity is lower on the Moon than on Earth. Which one of the following statements is true about the mass and weight of an astronaut on the Moon's surface, compared to Earth?
Mass is the same, weight is less.
Two men, Joel and Jerry, push against a car that has stalled, trying unsuccessfully to get it moving. Jerry stops after 10 min, while Joel is able to push for 5.0 min longer. Compare the work they do on the car.
Neither of them does any work.
When is the angular momentum of a system constant?
Only when no net external torque acts on the system.
Grandfather clocks are designed so they can be adjusted by moving the weight at the bottom of the pendulum up or down. Suppose you have a grandfather clock at home that runs slow. Which of the following adjustments of the weight would make it more accurate?
Raise the weight. (length of pendulum is dependent on period time)
Two simple pendulums, A and B, are each 3.0 m long, and the period of pendulum A is T. Pendulum A is twice as heavy as pendulum B. What is the period of pendulum B?
T (period is independent on mass)
Force F1 = 10 N @ 30∘ and force F2 = 8N @ 270∘. Use a sketch to determine the approximate direction of the resultant (vector sum) of F1 + F2. The resultant points into:
The 4th Quadrant ( add up all the x values together and all the y values together and then solve for the hypotenuse
Which one has larger kinetic energy: a 500-kg object moving at 40 m/s or a 1000-kg object moving at 20 m/s?
The 500-kg object calc both KE and check
Suppose that an object is moving with a constant velocity. Which statement concerning its acceleration must be correct?-
The acceleration is equal to zero
Two cyclists who weigh the same and have identical bicycles ride up the same mountain, both starting at the same time. Joe rides straight up the mountain, and Bob rides up the longer road that has a lower grade. Joe gets to the top before Bob. Ignoring friction and wind resistance, which one of the following statements is true?
The amount of work done by Joe is equal to the amount of work done by Bob, but the average power exerted by Joe is greater than that of Bob.
You throw a baseball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.
The work is negative on the way up and positive on the way down.
You are standing in a moving bus, facing forward, when you suddenly slide forward as the bus comes to an immediate stop. What force caused you to slide forward?
There is not a force causing you to slide forward.
When a rigid object rotates about a fixed axis, what is true about all the points in the object?
They all have the same angular acceleration.
In an air-free chamber, a pebble is thrown horizontally, and at the same instant a second pebble is dropped from the same height. Compare the times of fall of the two pebbles
They hit at the same time
If an object at rest remains at rest, then the sum of both the external torques and the external forces on the object must be zero. T/F
True
A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle θ below the horizontal, and the box remains a rest. The box rests on a horizontal surface that has some friction with the box. The normal force on the box due to the floor is equal to
W + P sin θ
The total mechanical energy of a simple harmonic oscillating system is
a non-zero constant.
If the answer to your calculation has units of kg ∙ m2/s, what type of quantity could it be?
angular momentum
A pilot drops a package from a plane flying horizontally at a constant speed. Neglecting air resistance, when the package hits the ground the horizontal location of the plane will
be directly over the package.
What is the frequency of the wave shown in the figure?
because it takes 2s to complete one cycle. f=1/t= .5Hz
Two displacement vectors have magnitudes of 5.0 m and 7.0 m, respectively. If these two vectors are added together, the magnitude of the sum
could be as small as 2.0 m or as large as 12 m.
Identical forces act for the same length of time on two different objects. The magnitude of the change in momentum of the lighter object is
exactly equal to the magnitude of the change in momentum of the larger mass.
Suppose a ball is thrown straight up and experiences no appreciable air resistance. What is its acceleration just before it reaches its highest point?-
exactly g
A simple harmonic oscillator oscillates with frequency f when its amplitude is A. If the amplitude is now doubled to 2A, what is the new frequency?
f. Amplitude is independent on frequency
What is the expression for frequency
f=1/T
If a stone is dropped with an initial gravitational potential energy of 100 J but reaches the ground with a kinetic energy of only 75 J, this is a violation of the principle of conservation of energy.
false. Not all of the PE has converted to KE
Jill does twice as much work as Jack does and in half the time. Jill's power output is
four times Jack's power output. (power=w/t)
A satellite encircles Mars at a distance above its surface equal to 3 times the radius of Mars. If gm is the acceleration due to gravity at the surface of Mars, what is the acceleration due to gravity at the location of the satellite?
gm /16
Two objects collide and bounce off each other. Linear momentum
is definitely conserved.
An object moving in the +x direction experiences an acceleration of +2.0 m/s2. This means the object
is increasing its velocity by 2.0 m/s every second.
Which of the following quantities are units of momentum?
kg ∙ m/s
Which of the following quantities are units of impulse?
kg ∙ m/s same as momentum
What is the expression for PE
mgh
You are making a circular turn in your car on a horizontal road when you hit a big patch of ice, causing the force of friction between the tires and the road to become zero. While the car is on the ice, it
moves along a straight-line path in its original direction
A player kicks a soccer ball in a high arc toward the opponent's goal. At the highest point in its trajectory-
neither the ball's velocity nor its acceleration are zero.
A car goes around a circular curve on a horizontal road at constant speed. What is the direction of the friction force on the car due to the road?
perpendicular to the curve inward
Two objects, one of mass m and the other of mass 2m, are dropped from the top of a building. If there is no air resistance, when they hit the ground Correct!
the heavier one will have twice the kinetic energy of the lighter one.
A merry-go-round spins freely when Diego moves quickly to the center along a radius of the merry-go-round. As he does this, it is true to say that
the moment of inertia of the system decreases and the angular speed increases.
If you stood on a planet having a mass four times that of Earth's mass, and a radius two times that of Earth's radius, you would weigh
the same as you do on Earth. ( see eqn 7)`
How much kinetic energy does a 0.30-kg stone have if it is thrown at 44 m/s
use kinetic energy eqn - 290J
When a certain string is under tension T, the speed of a wave in the string is v. What will be the speed of a wave in the string if the tension is increased to 2T without changing the mass or length of the string?
v*sqrt(2)
Swimmers at a water park have a choice of two frictionless water slides, as shown in the figure. Although both slides drop over the same height h, slide 1 is straight while slide 2 is curved, dropping quickly at first and then leveling out. How does the speed v1 of a swimmer reaching the bottom of slide 1 compare with v2, the speed of a swimmer reaching the end of slide 2?
v1 = v2
What is the expression for speed of a spring
v=sqrt(T/mu)
In simple harmonic motion, when is the speed the greatest?
when the magnitude of the acceleration is a minimum
When is the average velocity of an object equal to the instantaneous velocity
when the velocity is constant
A spaceship is traveling to the Moon. At what point is it beyond the pull of Earth's gravity?
It is never beyond the pull of Earth's gravity.
Suppose that an object travels from one point in space to another. Make a comparison between the magnitude of the displacement and the distance traveled by this object.-
The displacement is either less than or equal to the distance traveled.
When a guitar is tuned to adjust it pitch, what is it that is changed?
The frequency of the fundamental.
Which of the following statements is true about an object in two-dimensional projectile motion with no air resistance?
The horizontal acceleration is always zero and the vertical acceleration is always a non-zero constant downward.
A mass on a spring undergoes SHM. When the mass is at its maximum distance from the equilibrium position, which of the following statements about it are true?
The magnitude of its acceleration is a maximum.
An object is moving with constant non-zero velocity. Which of the following statements about it must be true?
The net force on the object is zero
A small car meshes with a large truck in a head-on collision. Which of the following statements concerning the magnitude of the momentum change during the collision is correct?
The small car and the truck experience the same magnitude momentum change.
A girl throws a stone from a bridge. Consider the following ways she might throw the stone. The speed of the stone as it leaves her hand is the same in each case. Case A:Thrown straight up. Case B:Thrown straight down. Case C:Thrown out at an angle of 45° above horizontal. Case D:Thrown straight out horizontally. In which case will the speed of the stone be greatest when it hits the water below if there is no significant air resistance? (Hint: Use Conservation of Mechanical Energy.)
The speed will be the same in all cases.
A disk, a hoop, and a solid sphere are released at the same time at the top of an inclined plane. They are all uniform and roll without slipping. In what order (first to last) do they reach the bottom?
sphere, disk, hoop
A rubber ball and a lump of clay have equal mass. They are thrown with equal speed against a wall. The ball bounces back with nearly the same speed with which it hit. The clay sticks to the wall. Which one of these objects experiences the greater momentum change?
the ball