BYU p121
the mud in elbonia is famous. filberts wants to bring home a 10 gallon bucket of this mud. estimate to the nearest order of magnitude, how much this bucket of mud would weigh. pure water (nothing like elbonia) weighs about eight pounds per gallon
100 lbs q1
the number of standard helium balloons that can be put into a minivan is closest to
200 cm1
partially inelastic collision is one where
momentum is conserved, KE is dissipated but not the maximum possible 9q
subtract 430.1 from 431.2 then multiply the result by 472.6, what determines the limit for sig fi
the fact that we subtract 430.1 from 431.2 cm1
choose which equation is dimensionally incorrect
v= x/4t + vo +at^2 q1
to convert the speed of 14.5 fulongs/fortnight to meters/second, you should multiply which of the following conversion factors times 14.5 furlongs/fortnights?
1 fortnight/14 days 1 day/86400 seconds 201.168 m/ 1 fulong cm1
which of the following principles makes it possible to calculate a vector sum by breaking the vector into its components?
1. sum of 2 vectors pointing in the same direction is in that same direction 2. magnitude of sum of 2 vectors in the same direction is equal to the sum of magnitude of the 2 vectors 3. magnitude of sum of 2 vectors in directly opposite directions is equal to the difference of magnitude of the 2 vectors 4. a vector perpendicular to a given vector has no component in the direction of the given vector cm3
a satellite moves in a very elliptical orbit, such that at the farthest point from earth it feels 1/4 the gravitational force that it feels at the nearest point to the earth. at that highest point, it has what fraction of the gravitational potential compared to the nearest point?
1/2 ( The potential goes as 1/r and the force goes as 1/r2. If the force is 1/4 of what it was, then the potential is 1/2 of it was because 1/4 is 1/2 squared.) cm13
The kinetic energy and potential energy of an oscillator in simple harmonic motion are equal to each other when the magnitude of the displacement from the equilibrium position is what fraction of the total amplitude?
1/sqrt2 q14
P=3iandQ=4j,theirsum P+2Q
3i+8j (P=3iand 2Q=8j) q3
We have two masses attracting each other due to their mutual gravitation. We double both masses and move them three times farther apart from each other. in this case the gravitation potential between them will be multiplied by a factor
4/3 the fact that the potential goes a 1/r instead of 1/r^2 means that the denominator will be 3. q13
We have two masses attracting each other due to their mutual gravitation. We double both masses and move them three times farther apart from each other. in this case, the gravitation force between them will be multiplied by a factor of
4/9 (F=(Gm1m2)/r^2 so if both m1 and m2 are doubled, that increases the force by a factor of 4. if r is triples then r^2 goes up by a factor of 9 so the final ratio is 4/9 q13
which of the choices represent the correct sig fig when adding: 42.045+ 1.51 + 1.717 + 0.4003
45.67 (limiting factor is the digits in the 3rd decimal place of 1.51 are unknown. in this addition problem we must cut off the digits at the third one after the decimal place q1
vectors A,B,C. A points west, B points north, C points due east. we don't know their relative magnitudes. we find the cross product of each these vectors with a vector which points due south D. rank the three cross products ( A*D, B*D, C*D) from smallest to largest in terms of their vertical component, taking the sign of the component into account
C*D, B*D, A*D ( The vertical component of ad is positive and that of cd is negative. bd is zero.) cm11
a set of two bars welded together can be rotated about any of axes. what is the order of moment of inertia of this object about each of these axes, from smallest to largest?
I,II,III (moment of inertia is greater when the mass is farther from the axis on average. for axis 1 only the short arm is long way from axis, axis ii only the long arm is long aways from axis, for axis iii both arms are a long ways from axis. this correct order puts more of mass successively farther from the axis as the sequence goes on) q10
Dilbert has gone to Elbonia to look at the latest version of their outsourced product. He finds that the power consumption of the device is rated at 2.5 swinepower by the Elbonians. He finds a reference book with the following conversion factors: I. 1 swinepower = 1 swinework/swineday II. 1 swinework = 25 kilojoules III. 1 swineday = 21600 seconds (about 6 hours - their swine sleep a lot) he wants to convert power consumption from swine power to watts, where 1 watt= 1 J/second. in order to do this he needs
Multiply 2.5 by 25000/21600 q1
[[A Volkswagen bug is moving to the right with a speed of 20 m/s. A large SUV is moving to the left at a speed of 20 m/s. The SUV has a mass three times that of the small car. They have an totally inelastic head-on collision in an intersection. There are two passengers in each vehicle, one seat-belted and the other not seat-belted. All the passengers weigh the same. The non-seat-belted passengers both collide with the dashboard of their respective cars. Use the following codes to refer to each of the passengers: SB = SUV, belted SN = SUV, non-belted VB = Volkswagen, belted VN = Volkswagen, non-belted]] rank the magnitude of the FORCES experienced by the four passengers in this collision, from SMALLEST TO LARGEST. if two forces are equal, then show an equals sign between them
SB<VB<SN<VN (both belted passengers will experience a smaller force because the time to change the momentum is much less if the passenger slows down with the car rather than hitting the dashboard. the time interval is probably 100 times shorter so the forces are at least 100 bigger. the momentum change is greater for the bug than the suv so the bug passengers will always have larger forces than the equivalent suv passengers. 9q
[[A Volkswagen bug is moving to the right with a speed of 20 m/s. A large SUV is moving to the left at a speed of 20 m/s. The SUV has a mass three times that of the small car. They have an totally inelastic head-on collision in an intersection. There are two passengers in each vehicle, one seat-belted and the other not seat-belted. All the passengers weigh the same. The non-seat-belted passengers both collide with the dashboard of their respective cars. Use the following codes to refer to each of the passengers: SB = SUV, belted SN = SUV, non-belted VB = Volkswagen, belted VN = Volkswagen, non-belted]] rank magnitude of IMPULSE experienced by four passengers in this collision from SMALLLEST to LARGEST.
SB=SN<VB=VN (both passengers in each car experience the same impulse, since it is equal to the change in the momentum. this requires from sb=sn and vb=vn. after the collision the two cars are moving in the direction of the suv at 10 m/s. this means that the passengers in the suv experienced a change in velocity of 10m/s while the passengers in the bus experienced a change in velocity of 30 m/s.
three axes of rotation. arrange order of smallest to largest moment of inertia for the object. all of the masses are the same and the rods are considered to be massless
The moment of inertia is the [[sum of the masses times their distances squared.]]] Since the masses are all the same, the distances are all that differ. The masses on average are closest to axis II because the horizontal arms are shortest. The masses are on average farthest from axis III because none of the masses lie on that axis. 10cm
in order to change the angular momentum of an object, it is necessary to apply
a net torque to the object ( A net torque produces a change in angular momentum. If you apply two equal and opposite forces to an object it is possible to have a net torque but no net force.) cm11
the center of mass of sword with a heavy hilt is located about 2 inches in front of the hilt. the blade is made of uniform density metal. the part of the sword to the right of the center of mass will have amount of mass relative to the part to the left of the hilt
a smaller amount of mass (sword made up of two masses, one equal to the mass on the right and the other equal to the mass on the left. the average position of the mass on the right is farther from the center of mass than the mass on the mass on the left. xcm= (m1x1+ m2x2)/ (m1+m2) and measuring distances from xcm so that the position of the center of mass is zero, we can see that if x2 is bigger than x1, then m2 must be smaller than m1) 9q
particle of mass .5kg has velocity of 2m/s. it is moving at constant velocity along a line that passes .5m away from origin, as shown below. rank the angular momentum of particle when it is at the points a, b, c from smallest to greatest. point a is 1.5 m away from point of closest approach, b is .5 m away and c is located at point of closest approach
a=b=c (since there is no torque here, angular momentum must be conserved. also l= r*p. since magnitude of L is mv r sin phi. but r sin phi= distance of closest approach= .5m. since mv doesn't change, neither does L.) q11
which of the following quantities is at a maximum when an object in simple harmonic motion is at its maximum displacement?
acceleration (when object is at max displacement, the velocity is zero, so KE is 0. the acceleration will be at max because the restoring force is at max when displacement is at max) q14
in this question vectors to the right are considered to be positive, while those to the left are considered negative. an object is moving to the left, but slowing down. which of the following statements is correct for that object?
acceleration is positive and velocity is negative (velocity is to the left so velocity is negative. the object is slowing down so the acceleration is in the opposite direction of the velocity so it must be positive) q2
which operation is not mathematically allowed?
addition of a vector and a scalar (a vector has direction and a scalar does not) cm3
which of the operations is not mathematically allowed?
addition of a vector to a scalar (vectors and scalars are different types of quantities and cannot be added. multiplication and division of a vector by a scalar gives a vector whose magnitude is multiplied or divided by the value of the scalar. two perpendicular vectors added all the time (right triangle) q3
a satellite is in circular orbit around the earth. if the speed of the satellite in its orbit suddenly increased by use of a rocket, without changing direction, the orbit will become
an ellipse with it maximum distance from the earth greater than the radius of previously circular orbit (the rocket increases the speed of the satellite. this means that gravity can no longer supply enough centripetal force to keep the satellite in its previous circular orbit so it moves in a larger arc. this means that the maximum distance will be greater than it previously was. all satellites move in elliptic orbits) q13
the gravitational force of the earth exerts no torque on satellite orbiting the earth in an elliptical orbit. compare the motion of the satellite at the point in its orbit nearest the earth to its motion at the point in it orbit farther from the earth. at these two points
angular momentum is the same (tangential and angular velocity will change as the satellite orbits. it loses and gains speed and KE as it moves farther from and closer to the earth. the thing that does not change is its angular momentum since there is no net torque) q11
a ball is thrown vertically upward takes 4 seconds to rise from the bottom of its path to its highest point. at what time is its instantaneous speed equal to the magnitude of its average velocity for the entire upward motion from bottom to top?
at two seconds into its motion (since the decrease in speed is linear, the average speed is halfway between the maximum and minimum speeds) q2
Steve is planning his annual Spring Break road trip. He pulls out his map and draws out his route to visit the five locations that he has planned for this year. They go in a counter- clockwise loop and he ends up at home, where he started, just in time to start classes again. Whenever he is on the road he travels a constant 60 miles/hour. when steve adds up the toal distance traveled, as measured by his odometer, and divides it by the time that his trip took, he has measured what quantity?
average speed (average speed is distance traveled along path traveled divided by the time) q2
whia driver on a trip recorded the reading on his odometer on his car at the beginning and end of his trip. he takes the difference between those two numbers and divides it by the time that the trip took. the quantity he has calulated
average speed cm2
two identical balls are thrown from the top of a cliff. one ball, ball A, is thrown straight up with speed v. the other, ball b, is thrown straight down with the same speed, v. which of the statements is correct?
ball A always has the same acceleration as ball b (the acceleration of any thrown object is always the acceleration of gravity downward, regardless of initial velocity. since the speed of ball a is decreasing and the speed of ball b is increasing after they are thrown. q2
when a pendulum swings with a small angel its motion is approximately simple harmonic. when it swings at at larger angel, why does this not work any more?
because acceleration is no longer proportional to the displacement ( The force, and therefore the acceleration, is proportional to the sine of the displacement, not the displacement. They are approximately equal at small angles, but become increasingly different at large angles.) cm14
it is easy to balance a bicycle when it is moving fast, but it is very difficult when it is stationary. the physical principle responsible for this effect is
conservation of angular momentum (spinning wheels act as gyroscopes, attempting to maintain their orientation at all times) q11
a body is made up of multiple parts that are attached to each other by several compressed springs. it has been shot from a cannon and at the peak of its trajectory the springs are released, causing the parts to fly apart. the center of mass of the two parts
continues along the same parabolic path as before 9cm
a body is made up of two parts that are attached to each other by a compressed spring. it has been shot from a cannon, and at the peak of its trajectory the spring is released, causing the two parts to fly apart. the center of mass of the two parts
continues along the same parabolic path it followed before (only external force on the two bodies is gravity and that is unchanged, the motion of the center of mass will continue as before) 9q
an isolated rigid body has a single force applied to it. from this we can conclude that it will
definitely have a linear acceleration and possibly have an angular acceleration ( F = ma requires an acceleration if there is a net force, as there must be in this case. If the force is applied at the center of mass then there would be no torque and therefore no angular acceleration. If the force is off the center of mass, then there would be an angular acceleration.) 10cm
in a two dimensional rectangular coordinate system, if the x component of a vector and the angel between the vector and x axis are known, then the total magnitude of the vector can be calculated by which of the following operations?
dividing the x component by the cosine of the angle (x component of vector is equal to magnitude times the cosine of the angle. x= Rcos theta so R=x/ cos theta) q3
an object starts with certain speed and slides with a friction on a horizontal surface until it comes to rest. which of the following would double the amount of time that it takes for an object to come to rest
doubling the initial speed of the object (the time it takes to stop is equal to the change in momentum divided by the force stopping it. if we double the mass, we double the momentum, but we also double the frictional force making the time be the same. if we double the speed we double the momentum and the force is unchanged. if we double the coefficient of friction, we double the frictional force, cutting the time in half) 9q
a bomb free of outside forces is traveling north when it explodes into exactly three pieces. one piece continues to travel north while another moves straight up relative to the ground. it is possible for the third piece to travel in a direction which is exactly
down (momentum must be conserved, so any momentum carried by any piece of the bomb that is not in the original direction must be cancelled by something carrying momentum in the opposite direction. one piece goes north, so it has nothing that must be cancelled. the piece that goes straight up has to have all of its momentum cancelled, since the initial state had no momentum in that direction) 9q
average speed of an object during a specified period of time is
equal to the magnitude of the average velocity for the same time period if the direction of motion does not change cm2
three vectors are added together. the magnitude of the resultant vector may be
equal to the sum of magnitude or less than the sum of magnitude depending on the circumstances (when three vectors are added together, they and their resultant must make a closed four sided figure. the resultant makes a straight line from the start to the end of the figure. since a straight line is the shortest distance between those two points, the magnitude of the resultant is less than the sum of magnitudes of the other vectors. for this case the answer is LESS than the sum of other vectors. if the 3 vectors are in the same direction however, then the magnitude of the resultant is equal to the sum of magnitude of vectors. EQUAL to the sum of other vecotrs q3
Steve is planning his annual Spring Break road trip. He pulls out his map and draws out his route to visit the five locations that he has planned for this year. They go in a counter- clockwise loop and he ends up at home, where he started, just in time to start classes again. Whenever he is on the road he travels a constant 60 miles/hour. s steve's average velocity for the whole trip
exactly zero (average velocity is defined as displacement from starting point to ending point divided by time. since he started and ended in same place, displacement is zero, so avg velocity is zero) q2
when a car tires rotates about a fixed axis, every portion of the wheel
has same angular velocity, but different centripetal acceleration (angular velocity is same everywhere. the centripetal acceleration depends on the radial position ac=rw^2) q10
when a car tire rotates about a fixed axis, every portion of the wheel
has the same angular velocity, but different centripetal acceleration ( Every point on a rigid body has the same angular velocity, w. The centripetal acceleration depends on radius: ac = r w2.) 10cm
an astronaut who is floating freely through space is seated upon a unicycle. he begins to pedal the unicycle forward. as he does so
he begins to rotate in the opposite direction that his unicycle wheel rotates (there are no external torques, angular momentum must be conserved. if the wheel starts to rotate in one direction and therefore gains angular momentum, he must start to rotate in the opposite direction to create an equal amount of oppositely directed angular momentum) q11
A figure skater has very little friction with the ice. She can change her rate of rotation by drawing in her outstretched arms. we can understand this effect by observing that
her angular momentum remains constant in this process q11
a driver who is protected by an airbag during a head on collision is less likely to be seriously injured than an unprotected driver. this is so because the airbag
increases the time interval over which the impulse is experienced (impulse and change in KE are unchanged by the presence of the airbag. the driver still has to go from initial velocity to zero velocity, which determines his change in KE and his impulse. making collision more elastic would be a bad thing, as it would require the driver to rebound, which would increase the impulse) 9q
a driver who is protected by an air bag during a head-on collision is less likely to be seriously injured than an unprotected driver. this is because the airbag
increases the time interval over which the impulse is experienced 9cm
a bullet moving horizontally strikes and sticks in a block of wood that is free to move on the horizontal, level, frictionless surface. the block has a much greater mass than the bullet. what becomes of most of the momentum of the bullet
it becomes total momentum of the block plus the bullet 9cm
bucket hangs into a well from a rope. the rope is wound on a spool of radius r. as the bucket is brought up the rope wraps around the spool, increasing the radius at which the rope winds. if the spool is rotated at a constant angular speed, what happens to the speed of the bucket as it comes up?
it increases ( The speed of the rope on the spool is w r, so if r increases and w remains constant, the speed must increase.) 10cm
a rocket blasts off from earth on its way to the moon. as the rocket travels, it loses mass burning fuel and ejecting stages of the rocket. when the mass of the rocket has been reduced to one-half of its original mass it has traveled a distance equal to the radius of the earth away from the surface of earth where it took off. at this point, how does the gravitational force between rocket and earth compare to the gravitational force at lift off?
it is 1/8 of what it was at lift off ( The mass has been reduced by a factor of two and the distance has been doubled. Using Newton's gravitation equation, we get a factor of one-half for the mass decrease and another factor of one-fourth for the distance being one-half and then being squared.) cm13
suppose there is an object which is subject to a force which follows the relation F=+kx. what will happen to the object if it si moved away from the equilibrium position (x=0) and released?
it will move farther away with increasing acceleration (the force is away from equilibrium position and the force will increase as the body moves farther away. that means the accerlation will increase as the object moves farther away) q14
A pendulum is made of a very long string with a hollow ball filled with water attached to the end. The ball and the water have equal masses. There is a small hole in the ball and water slowly leaks out. What happens to the frequency of the pendulum as the water leaks?
it will stay constant (frequency of pendulum doesn't depend on mass of pendulum, it only depends on the strength of gravity and length of string. in analyzing forces the mass decreased but the restoring force decreased by a proportional amount to the amount decrease) q14
We have two masses attracting each other due to their mutual gravitation. We double both masses and move them three times farther apart from each other. will it take more or less work to separate the two masses out to infinity after the change has been made
it will take more work to separate the two masses after the change (the work done to separate them to infinity is equal to the potential energy. the potential energy has increased by a factor of 4/3 so it takes more work to separate them now q13
A figure skater has very little friction with the ice. She can change her rate of rotation by drawing in her outstretched arms. when she draws in her arms, which of the following results?
larger rotational rate (angular momentum is conserved, since there are no external torques. by drawing in her arms she reduced her moment of inertia. to keep l=iw constant her angular velocity must increase q11
the period and radius of the orbit of satellites around a planet can be used, along with keeper's third law to determine the ___ of the parent planet.
mass (period radius relationship in keeper's third law is inversely proportional to the mass of the central body) q13
the amplitude of an object experience SHM is doubled. which of the following is also doubled?
maximum velocity (when double the A we quadruple the total energy of the oscillation since PEmax= .5kA^2. the frequency and period are unchanged by the change in amplitude. the max KE is also quadrupled since energy is conserved. this mean max velocity is doubled q14
if a two body collision is not head on, then which of the following is ALWAYS true
momentum is conserved (momentum is always conserved in collisions. whether or not it is head on is not relevant. momentum conservation is a vector law, so momentum is conserved separately in each direction. KE is sometimes conserved, but not always.) 9q
a totally elastic collision is one where
momentum is conserved and kinetic energy is conserved (momentum is always conserved. an elastic collision is one where KE is conserved) 9q
a totally inelastic collision is one where
momentum is conserved, but KE is dissipated as much as possible (momentum is conserved but totally inelastic means the two stick together) 9q
why is not possible to sit upright in a chair then raise to ones feet without first leaning forward?
one has to move the center of gravity of the body over the feet before one can stand up while maintaining equilibrium (if you attempt to stand up without moving center of gravity over feet, the torque due to gravity will cause you to fall back, since there is no other force available to counteract that torque) q12
suppose a special spring is made that has an unusual force law. the force law of this spring is F=-kx^3. the motion of mass attached to this spring will be
periodic motion, but not simple harmonic motion (You only get simple harmonic motion for Hooke's Law type forces, i.e. F = -kx. You get periodic motion with any kind of force law which is a restoring force that doesn't change in time.) cm14
as you drive your car down the road, you notice a rattle in one of the doors. you notice that it is worst at 35mph. when you are going either 25 or 45 it doesn't rattle much at all. this is most likely a consequence of
resonance (The speed dependence of the rattle is explained by resonance. When you are going slowly the car shakes the door too slowly to cause the rattle. When you are going fast the frequency is too high for the rattle. When you are going 35, the frequency is just right.) cm14
x component of given vector is equal to that vector magnitude multiplied by which function below given theta is the angle between the vector and the y axis?
sin theta (the sine function is the opposite over the hypotenuse, so given which angle is defined as theta, this is the correct choice) cm3
There are four objects that can be rolled down a ramp. They are a hollow cylinder, a solid cylinder, and two spheres. They all have the same total mass and the same radius. One of the spheres has a special anti-friction coating, so it slides down the ramp instead of rolling. We start them all down the ramp at the same time. The moment of inertia of a sphere is 2/5 m r2, that of a cylinder is 1/2 m r2, and that of the hollow cylinder is m r2. which of the objects arrives at the bottom first?
sliding sphere (sliding sphere puts none of its potential energy into rotation, so it all goes into translational KE, therefore it goes the fastest. all the others have to put some of their PE into rotational KE) q10
a body falls freely from rest, straight downward. it has a constant acceleration of 9.8. this means that the m/s2
speed of the body increases 9.8 m/s during each second that it falls cm2
a solid sphere A rolls down an inclined plane, while an identical sphere, B slides down the plane without friction. they start from the same height. which of the following happens?
sphere B arrives first ( For sphere A the potential energy gets partly converted into rotational kinetic energy, leaving less for the translational part of the kinetic energy, thus slowing it down. For sphere B it all becomes translational kinetic energy. Thus B arrives before A.) cm10
a box of mass m is sitting on a frictionless table. it has a rope attached to it that goes over a massive pulley, of moment of inertia I. there is no friction in the bearing of the pulley. the rope then hangs down from the pulley to a mass m2 which hanging freely. the hanging mass is allowed to fall, pulling m1 towards the pulley. the tension in the rope pulls on m1 with force t1. the rope pulls on m2 with a force of t2. which of the following is true about t1 and t2
t1 is less than t2 (the pulley must be accelerated in clockwise direction. there are two torques acting on the pulley, the torque due to t2 clockwise and toque due to t1 counterclockwise. the clockwise torque must be bigger. since the moment arm for both forces is the same, the difference in torque must be due to the difference in magnitude of forces and t1<t2) q10
a rock is thrown upward from the top of a tower. it rises at first and eventually falls to the ground at the base of the tower. at what point in its motion is its acceleration least?
the acceleration is the same at all points in the motion of the rock cm2
when a catcher in baseball catches a fast ball, he does not hold his arms rigid, but relaxes them so that the mitt moves serval inches with the ball while the ball is being caught. the action results in which of the following?
the average impact force is made smaller by increasing the time interval (total momentum and energy absorbed is the same regardless of what he does. this means that the impulse received is the same also. the only thing he can change is how much force his hand feels by increasing the time interval) 9q
we have two vectors that line in the x-y plane. if we take the cross product of those two vectors were know that
the cross product vector will be either in the z+ or z- direction (the magnitude of the cross product will be equal to the product of two magnitudes times the sine of the angel between the,. if the angle is 90 then the magnitude is equal to the product of the magnitudes. if the angle is less than 90, then the magnitude is smaller. the magnitude can never be greater than the product of the magnitude. the cross product is perpendicular to both vectors, so it must not be in the x-y plane. the only direction perpendicultar to two non par allel vectors in the x-y plane is the +/- z direction q11
imagine you are designing a small car and you want to make it as safe as possible. there are two ways that you can design the car for a collision. one is to make it so that the car will crumple up and come to rest along with the other vehicle. the other method is to make the car very rigid so that it will bounce off of the other vehicle. which method will be safer to use
the crumple method, because the force experiment by the passengers will be less in this case (the force will be less because the same impulse is applied over a longer period of time, making it so that the force can be less) 9q
a feather and iron ball are suspended inside a vacuum chamber. the feather is half a meter farther from the ground than the iron ball. the feather is dropped and just when it is even with the iron ball the iron ball is dropped. which reaches the ground first, the feather or the iron ball?
the feather will hit the ground first (the feather has a non-zero speed when the iron ball is dropped, it will always have a higher speed than the ball. they both have the same acceleration, which is the rate of increase in the speed. because the feather always has a higher speed, it will make it to the ground first) q2
consider a ladder leaning against a wall and pick the axis of rotation to pass through the point where the bottom of the ladder touches the ground. the weight of the ladder exerts a torque about this axis. what other forces on the ladder will also exert a torque about this same axis?
the forces of friction with the wall AND the normal force on top of the ladder where it touches the wall (axis of rotation is at bottom of ladder, the moment arm for any force acting at the bottom will be zero regardless of its direction. all forces acting on the other end will exert torques, unless they point straight down the ladder or straight away along the length of the ladder) q12
the amplitude of a simple harmonic oscillator is doubled.which of the following remain the same?
the frequency (The frequency depends only on the spring constant and the mass, not the amplitude.) cm14
There are four objects that can be rolled down a ramp. They are a hollow cylinder, a solid cylinder, and two spheres. They all have the same total mass and the same radius. One of the spheres has a special anti-friction coating, so it slides down the ramp instead of rolling. We start them all down the ramp at the same time. The moment of inertia of a sphere is 2/5 m r2, that of a cylinder is 1/2 m r2, and that of the hollow cylinder is m r2. which object arrives last at the bottom?
the hollow cylinder the one with greatest rotational KE will have smallest translational KE, and therefor slowest speed q10
There are four objects that can be rolled down a ramp. They are a hollow cylinder, a solid cylinder, and two spheres. They all have the same total mass and the same radius. One of the spheres has a special anti-friction coating, so it slides down the ramp instead of rolling. We start them all down the ramp at the same time. The moment of inertia of a sphere is 2/5 m r2, that of a cylinder is 1/2 m r2, and that of the hollow cylinder is m r2. which of the objects has greatest rotational KE when it arrives at the bottom?
the hollow cylinder (larger the moment of inertia relative to the mass the larger the fraction of energy that goes into rotational KE. since all of them have the same total energy, the hollow cylinder have the largest rotational KE
two vectors P and Q. the definition of P is P= i *(i*j). the definition of Q is Q= (i*i)*j
the magnitude of P is greater than the magnitude of Q (magnitude of Q is 0, because i*i=0. P on the other hand has magnitude of 1, because it is equal to -j q11
a rocket fully loaded with fuel is fully loaded with fuel is sitting in space far from any other body. the engine is started and the rockets starts to spew exhaust gases out of the back of the engine. which of the following explains what happens?
the momentum of the exhaust gases must be equal to the momentum gained by the rocket. 9cm
consider a bicycle parked on a hill and pick the axis of rotation to pass through the point where the front tire touches the ground. the weight of the bicycle exerts a torque about this axis. what other forces on the bicycle will also exert a torque about this axis?
the normal force on the back wheel only cm12
an object weighs slightly less on a mountain peak than near the base of the same peak. this is primarily because
the peak is slightly further from the earth's center, thus g is slightly less there q13
if a mass of a spring and pendulum have same period on the moon where the gravity is 1/6 value on earth, which one will run faster on earth?
the pendulum (the mass on the spring will not change its frequency since it doesn't depend on g. the pendulum however will speed up because its dependence on g) q14
for three vectors to add up to zero, what must be true of the magnitude of the three vectors?
the sum of two magnitudes must be greater than or equal to the third for all three vectors cm3
if only two forces act on a body and the body is in status equilibrium, which of the statements must be true?
the two forces are equal in magnitude and opposite in direction. AND the two forces act along the same line (two forces must be equal in magnitude and opposite in directions to satisfy the first condition of equilibrium that all forces must cancel. the second condition that the torques must cancel, requires that they act along the same line. if they acted along different lines, then they would create a net torque ) q12
a cylinder is experiencing no angular acceleration(a'). by this we can be certain that
there can be forces acting on the cylinder, and they can cause torques, but the torques must cancel (angular acceleration is equal to the net torque divided by the moment of inertia. if there is no a' that only tells us that there is no net torque. therefore if we have multiple forces they can all cause torque if the torque cancels out) q10
There are four objects that can be rolled down a ramp. They are a hollow cylinder, a solid cylinder, and two spheres. They all have the same total mass and the same radius. One of the spheres has a special anti-friction coating, so it slides down the ramp instead of rolling. We start them all down the ramp at the same time. The moment of inertia of a sphere is 2/5 m r2, that of a cylinder is 1/2 m r2, and that of the hollow cylinder is m r2. which object has greatest total KE when it arrives at bottom?
they all have the same total KE (since they all have the same PE to begin with, they will all have the same total KE at the bottom. the only thing that will be different will be how it is divided among the two types of KE) q10
pendulum a has a mass of 100g and pendulum b has a mass of 250 g. they have the same length. the pendulum with the longest period would be
they will have the same period. (The period of a pendulum doesn't depend on its mass, just the length of the string and the acceleration of gravity.) cm14
how many scalar quantities are in the list
three temperature speed mass (velocity and acceleration are vectors) q3
block A is traveling due north with a velocity of 10m/s. block B is traveling due east with a velocity of 1m/s. block A has 10 times the mass of block B. the two blocks stick together after the collision. after the collision the two blocks
travel slightly east of north 9cm
Dilbert has gone to Elbonia to look at the latest version of their outsourced product. He finds that the power consumption of the device is rated at 2.5 swinepower by the Elbonians. He finds a reference book with the following conversion factors: I. 1 swinepower = 1 swinework/swineday II. 1 swinework = 25 kilojoules III. 1 swineday = 21600 seconds (about 6 hours - their swine sleep a lot) how many sig figs are there in the final result of that conversion
two (initial data (2.5) has two sig figs. the conversions have at least that much accuracy, so limiting factor is initial data q1
an object is thrown straight up and then eventually comes down. at its highest point
velocity is zero and acceleration is downward not zero (velocity is 0 because it is neither moving up or down. the acceleration is downward, like it is throughout the motion. you can tell acceleration is downward because a moment before the object reached the top it was moving up and a moment after it reaches the top is will be moving down. the change in the velocity is downward, so the acceleration is downward) q2
constant acceleration. we had an object with an acceleration that increased linearly with time, a(t)= a0t. which of the equations below is not one of the equations of motion for this case?
vf2^2= vi^2 + 2a0(dx) cm2
a disk is spinning in a clockwise direction and is speeding up. if dtheta is positive for a counterclockwise rotation, then the signs of w and a' must be
w must be negative and a' much be negative if counterclockwise is positive, then clockwise rotation must be negative w. since it is speeding up, the angular acceleration(a') must have the same sign as w q10
a spinning circular saw blade has two marks on it, one at the outer edge (a) and one halfway to the middle of the blade (b). as the saw blade speeds up from rest, which of the following is true about the angular velocity of mark a and make b(wa and wb) and tangential velocity of mark a and mark b (va and vb)?
wa=wb, va=2vb (the angular v is same everywhere. the tangential velocity is proportional to the radius, so outer rim is moving twice as fast and the halfway point) q10
an artificial earth satellite is in an elliptical orbit with the earth at one focus. it has the greatest speed
when it is nearest the earth ( By Kepler's second law it sweeps out equal areas in equal times. When it is closest to the Earth the radius is smallest, so the speed it travels must be greatest.) cm13
in solving a problem involving a board and a box in static equilibrium, where must be put the axis of rotation that we use for calculating the torques
wherever we want to (the axis of rotation can go anywhere. if an object is not rotating, it is not rotating around any axis we choose. any of the choices above a good choices for the axis of rotation, but we don't have to put it anywhere) q12
in solving a torque balancing homework problem for a beam in static equilibrium, where must we put the axis of rotation?
wherever we want to cm12
which of the equations below is in error, as shown by dimensional analysis?
x= not + at/2 cm1
R=3i−7j. Which of the vectors below can we addto R to get a vector that points purely in the y-direction?
−3i−4j (add vector that has an x component that cancels that of R. the sum would be -13j) q3
