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Which of the following gives the correct dimensions for the unit of force. Recall that length = L , mass = M, and time = T - a. M L / (T^2) Which of the following is not a fundamental (aka a field) force? - the force of forward motion also known as the inertial force What is the definition of mass? - The resistance of an object to acceleration if it is otherwise able to freely move What property of a body resists acceleration? - its mass The force required to accelerate a 2.0 kg mass at 4m/s2 is - 8 N What force will be needed to accelerate an 4 kg mass at the same acceleration as a 2 kg mass? - double the force A cart is uniformly accelerating from rest.The force on the cart must be - constant In the graph below, the acceleration of an object is plotted against the unbalanced force applied. What is the mass of the object? - .5 kg What is the net force (magnitude and direction) of the object depicted in the following free body diagram? (Ftension = 1200 N & Fgravity = 800 N) - 400 N up Two boxes are pushed with the same amount of total force. One has a mass of 1kg and the other 100kg, which one will accelerate faster? - the 1 kg mass You push an object, initially at rest, across a frictionless floor with a constant force for a time interval Δt, resulting in a final speed of v for the object. You then repeat the experiment, but with a force that is half as large. What time interval is now required to reach the same final speed v? - 2 Δt An object experiences no acceleration. Which of the following CANNOT be true for the object? - A single external force acts on the object. A student is moving into the dorm. She chooses to push one particularly large box across the floor. As she is pushing at a constant speed, she must supply a force that - that is the same as the total of the forces resisting the motion of the box
As the space shuttle takes off, you can see it accelerating off of the ground. This tells you that - that there is a net force acting on the rocket. In addition, the sum of these forces is positive, causing the rock to move in the up (or positive) direction Suppose you are one of the first to live on a lunar colony. You call one of your friends, who still lives on the Earth, to tell him that you have just won a newton of gold in a contest. Excitedly, he tells you that he entered the Earth version of the same contest and also won a newton of gold! Who is has won more? (Assume that the price is the same on both the moon and the Earth and measured in terms of the mass of gold). - You (on the moon) won more A bumper car is moving at constant velocity when another bumper car starts to push on it with a constant force at an angle of 60 degrees with respect to the first car's initial velocity. The second bumper car continues pushing in exactly that direction for some time. What is most likely to happen is that - the first car's velocity will gradually change direction more and more toward that of the force while increasing in magnitude. A constant force is applied to a body that is already moving. The force is directed at an angle of 60 degrees to the direction of the body's velocity. What is most likely to happen is that - the body will gradually change direction more and more toward that of the force while speeding up. Aline and Charlie are arguing as to whether or not it is possible in principle for an elevator to have an acceleration of magnitude greater than g. In the course of their discussion they come up with the statements below. Which one is correct? - Yes, because it can reach an acceleration greater than g if the motor is strong enough. The apparent weight of a fish in an elevator is greatest when the elevator - accelerates upward The first of two identical boxes of mass m is sitting on level ground. The second box is sitting on a ramp that makes a 20° angle with the ground. The normal force of the level ground on the first box is NL; the normal force of the ramp on the second box is NR. Which statement is correct? - NL = mg; NR = mg cos 20° Two people, each of 70 kg mass, are riding in an elevator. One is standing on the floor. The other is hanging on a rope suspended from the ceiling. Compare the force FF the floor exerts on the first person to the force FR the rope exerts on the second person. Which statement is correct? -. They are equal and have the same direction. When an acrobat hangs motionless from a pair of rings - she exerts a gravitational force on the Earth that is equal to the sum of the forces the rings exert on her. You have a machine which can accelerate pucks on frictionless ice. Starting from rest, the puck travels a distance x in time t when force F is applied. If force 3F is applied, the distance the puck travels in time t is - 3x
You throw a ball up in the air and hold your hand under it to catch it when it comes down. The reason why the ball stops is because - your hand exerts a force on the ball in the direction opposite to its velocity. A book is placed on a chair. Then a videocassette is placed on the book. The floor exerts a normal force - only on the chair The normal force is always equal to the weight of the object on the surface. - fasle A flat sheet of paper is dropped from the top of a building. Assume the force exerted on the paper by the Earth is the same strength as the force from the drag force of the air. The paper ________ - moves at a constant speed Which of these will help a Formula 1 car go faster? - better streamlining You work for a moving company and need to lift a piano to the third floor. To preform the lift you choose to use a single simple pulley, located just under the roof at the fourth floor. (Assume a frictionless and mass-less pulley and a mass-less rope). To accelerate the the piano off the ground, you must a apply a force that is ________ the weight of the piano. - greater than The apparent weight of a fish in an elevator is greatest when the elevator - accelerates upwards Which of the following surfaces has the largest amount of static friction against your skin? Which one has the highest coefficient of static friction against your skin? - sandpaper You press your physics textbook flat against a vertical wall with your hand. What is the direction of the friction force exerted by the wall on the book? - upward A friction force is _____________ - a contact force that acts parallel to the contact surface. To make an object start moving on a surface with friction requires - more force than to keep it moving on the surface The frictional force of the floor on a large bag is least when the suitcase is _________ - pulled by a force directed at an angle, Θ, above the floor. The first of two identical boxes of mass m is sitting on level ground. The second box is sitting on a ramp that makes an angle with the ground. When a force of magnitude F is applied to each box in a direction parallel to the surface it is on, upwards for the box on the ramp. Neither box moves. The coefficient of friction between the box and the ground & the box and the ramp are the same. Which of the following statements comparing the
friction force on the box on the level, {f_L}, to the friction force on the box on the ramp, {f_R}, is correct? - f(R) <f(L) The total force needed to drag a box at constant speed across a surface with coefficient of kinetic friction mk is least when the force is applied at an angle q such that - tanq = mk. The frictional force of the floor on a large suitcase is least when the suitcase is - pulled by a force directed at an angle q above the floor. When you drag a toy teddy bear along the floor by a force that is parallel to the floor, the magnitude of the force of friction - is independent of velocity or acceleration Which of the following do NOT effect the drag force on an object passing through a fluid media? - The material of the object You are in a skydiving troupe and wish to form a human ring in the air composed of all six of you. You are the last on the leave the plane. To meet those who left the plane before you, you should - dive to minimize your cross-sectional area Jill holds a bowling ball in a fixed position. The work she does on the ball ____ - it is equal to zero The ability to do work is called _________ - energy Negative work can be done - only by (b) and (c) above (by a spring at the bottom of an elevator shaft when it stops a falling elevator.) (by a hand catching a ball.) The force of static friction exerted on an automobile's tires by the ground - provides the accelerating force that makes the car move forward. Two balls, A and B, of mass m and 2m respectively, are carried to height h at constant velocity, but B rises twice as fast as A. The work the gravitational force does on B is - twice the work done on A. When a ball rises vertically to a height h and returns to its original point of projection, the work done by the gravitational force is - 0 Carts A and B have equal masses and travel equal distances on straight frictionless tracks while a constant force F is applied to A, and a constant force 2F is applied to B. The relative amounts of work done by the two forces are related by - W(B)= 2 WA Jane and Jake are looking at what happens to body 1 of mass m and body 2 of mass 2m, initially at rest, when equal forces are applied separately to the two bodies. Jake says that equal forces applied for equal times do equal amounts of work on the two
Both carts start from rest. The velocities vA and vB of the bodies at the end of distance D are related by - vB = √2 vA. Equal amounts of work are performed on two bodies, A and B, initially at rest, and of masses M and 2M respectively. The relation between their speeds immediately after the work has been done on them is - vA = √2 vB. Two clowns are launched from the same spring-loaded circus cannon with the spring compressed the same distance each time. Clown A has a 40-kg mass; clown B a 60-kg mass. The relation between their kinetic energies at the instant of launch is - K(A)=K(B) Two clowns are launched from the same spring-loaded circus cannon with the spring compressed the same distance each time. Clown A has a 40-kg mass; clown B a 60-kg mass. The relation between their speeds at the instant of launch is - v(A)=radical3/2(vb) Two eggs of equal mass are thrown at a blanket with equal velocity. Egg B hits the blanket but egg A hits the wall instead. Compare the work done on the eggs in reducing their velocities to zero. - The amount of work is the same for both. Two identical arrows, one with twice the kinetic energy of the other, are fired into a hay bale. The faster arrow will penetrate _______ - twice as far as the slower arrow. If the speed of a particle is doubled, what happens to its kinetic energy? - It becomes 4 times larger A certain truck has twice the mass of a car. Both are moving at the same speed. If the kinetic energy of the truck is K, what is the kinetic energy of the car? - K/ Kinetic energy is the energy ___ - motion An object that has kinetic energy must be _________ - moving What is the sign on kinetic energy? - The sign is always positive Mark and Susan are loading identical cement blocks onto David's pickup truck. Mark lifts his block straight up from the ground to the truck, whereas Susan slides her block up a ramp on a massless, frictionless roller ramp. Which statement is true? - Mark and Susan do the same amount of work An ordinary red Ford 1999 F150 pickup truck is traveling down Dodge Street at speed v. An identical F150 pickup (except it is blue) is traveling at speed 2v. The kinetic energy of the blue truck is _______ - four times that of the red truck The value of kinetic energy can be negative. - false
An object that has potential energy may have potential energy because of its ________
- location An object at rest may have - energy Cubical blocks of mass m and side l are piled up in a vertical column. (Assume that the potential energy is located at a point in the center of the block.) The total gravitational potential energy of a column of three blocks is - (9/2) mgl. What is the sign on the gravitational potential energy? - The sign can be positive or negative. The force a spring exerts on a body is a conservative force because - the net work a spring does on a body is zero when the body returns to its initial position The potential energy of a spring is __________ - proportional to the square of the amount the spring is stretched A compressed spring is used to launch a skier across an icy flat. How far across the incline the skier travels depends on all but which of the following factors: - the value of the gravitational constant g at this location. A dart is loaded into a spring-loaded toy dart gun by pushing the spring in by a distance x. For the next loading, the spring is compressed a distance of 2x. How much work is required to load the second dart compared with that required to load the first? - four times as much A dart is loaded into a spring-loaded toy dart gun by pushing the spring in by a distance x. For the next loading, the spring is compressed a distance of 2x. How much faster does the second dart leave the gun compared with the first? - two times as much A small lead sphere of mass m is hung from a spring of spring constant k. The gravitational potential energy of the system equals zero at the equilibrium position of the spring before the weight is attached. The total mechanical energy of the system when the mass is hanging at rest is - - 1/2 k(x^2) The energy of a projectile flying through the air is _____ - both kinetic and potential energy A car that travels twice as fast as another identical car when braking to a stop will skid _______ - four times as far A rock of mass m is dropped to the ground from a height h. A second rock, with mass 2m, is dropped from the same height. When the second rock strikes the ground, what is its kinetic energy with respect to the other rock? - The kinetic energy is twice as much.
An astronaut tosses a ball out in space where gravitational forces may be neglected. What will happen to the ball? - It will be slowed down very gradually by collisions with molecules in space. Any change of the energy of a system occurs because of - energy transfer across the boundaries of the system. Identical masses m are attached to identical springs of spring constant k suspended from the ceiling. With both masses hanging in their equilibrium positions, mass A is pulled down 10 cm and released while mass B is pushed up 10 cm and released. Which statement is correct? - Masses A and B will travel equal distances between their highest and lowest points Two cannonballs are dropped from a second floor physics lab at height h above the ground. Ball B has four times the mass of ball A. When the balls pass the bottom of a first floor window at height h/4 above the ground, the relation between their kinetic energies, KA and KB, is - KB = 4KA An example of a system having both kinetic and potential energy would be - an object in free fall Two masses, MA and MB, with MB = 2MA, are released at the same time and allowed to fall straight down. Neglect air resistance. When we compare their kinetic energies after they have fallen equal distances, we find that - KB = 2KA. Consider a block sliding over a horizontal surface with friction. Ignore any sound the sliding might make. If you were to define an isolated system, the system would include - the block and the surface Three identical balls are thrown from the top of Hennessy, all with the same initial speed. Ball 1 is thrown horizontally, ball 2 is thrown at 45 degrees above the horizontal, and ball 3 is thrown at 45 degrees below the horizontal. What is the relationship between the speeds of the balls when they hit the ground. - v.1 = v.2 = v. For a force to be a conservative force, when applied to a single test body, - the net work done for motion in a closed path is zero. If you push an object with twice the work input for twice the time, your power input is _____ - the same amount as for half the work in half the time. Tom and Becky race up a hill. Tom's weight is 180 lb and Becky's weight is 135 lb. The race is a tie. Who uses more power climbing the hill? Assume that they both operate at the same metabolic efficiency. Select one: - tom
If you do work on an object in half the usual time, your power output is - twice the usual power output A car of mass m1 traveling at velocity v passes a car of mass m2 parked at the side of the road. The momentum of the system of two cars is - m(1)v The value of the momentum of a system is the same at a later time as at an earlier time if there are no - external forces acting on particles of the system. If the speed of a moving object doubles, then what else doubles? - momentum Which of the following has the largest momentum relative to earth? - A pickup truck speeding along a highway An airbag (in conjunction with a seat-belt) will lessen the injuries caused by a car accident. How does the airbag do this, compared to wearing a seat-belt only? - By increasing the time duration of impact An impulse of 50 N*s is applied to each of two objects of different masses that are initially at rest. Which object has the greatest velocity change? - the less massive object The area under a F-t graph represents.. - impulse It is correct to say that impulse is equal to _______ - the change in momentum Two objects of different masses are initially at rest, and then undergo the same velocity change. Which object experienced the greater impulse? - the more massive object Two objects have equal kinetic energies. How do the magnitudes of the their momenta compare? - There is not enough information to tell. A truck is chasing a bicycle along a highway. Both have the same momentum. Which of the following is true? - The bicycle will outrun the truck Your physical therapist throws a baseball to you at a certain speed and you catch it. To increase the difficulty, the therapist is going to throw you a medicine ball whose mass is ten times the mass of the baseball. You are given the following choices. Rank these from easiest to hardest to catch.
- The medicine ball thrown at the same speed as the baseball
- The medicine ball thrown with the same momentum as the baseball.
- The medicine ball thrown with the same kinetic energy as the baseball - 2 (same p), 3 (same K), 1 (same v) A ball of clay of mass m is thrown with a speed v against a brick wall. The clay sticks to the wall and stops. The principle of conservation of momentum is violated in this example. - false
The law of conservation of momentum applies to a collision between two bodies if ________ - they exert equal and opposite forces on each other. A car and a large truck traveling at the same speed collide head-on and stick together. Which vehicle undergoes the larger change in the magnitude of its momentum? - the car A car and a large truck traveling at the same speed collide head-on and stick together. Which vehicle undergoes the larger change in the magnitude of its velocity? - the car A steel ball bearing of mass m1 and speed of magnitude v1 has a head-on elastic collision with a steel ball bearing of mass m2 at rest. Rank the speed v1 of m1 relative to v2, the magnitude of the speed of m2, after the collision when i) m1 > m2; ii) m1 = m2; and iii) m1 < m2. -. v1 < v2; v1 = v2; v1 > v Car A rear ends Car B, which has twice the mass of A, on an icy road at a speed low enough so that the collision is essentially elastic. Car B is stopped at a light when it is struck. Car A has mass m and speed v before the collision. After the collision _________ - the momentum of car B is four times as great in magnitude as that of car A. You are practicing playing pool. The cue ball just barely hits the eight ball. For this collision, - momentum is conserved in the direction perpendicular to as well as parallel the cue ball's initial velocity. While playing eight ball with a friend, you need to sink the final ball. This ball side just beside the pocket. One of your choices is to shoot the cue ball directly at the three ball. Assuming the masses of the two balls are the same and you execute the shot perfectly (and not also sink the cue ball), the cue ball will ______ - stop and the three ball will move with the cue ball's initial velocity Car A rear ends Car B, which has twice the mass of A, on an icy road at a speed low enough that the collision is essentially elastic. Car B is stopped at a light when it is struck. Car A has mass m and speed v before the collision. After the collision, - the momentum of car A is four times as greater in magnitude as that of car B When two bodies of different masses collide, the impulses they exert on each other are
- equal but opposite for all collisions. In a perfectly inelastic one-dimensional collision between two moving objects, what condition alone is necessary so that the final kinetic energy of the system is zero after the collision? - The objects must have momenta with the same magnitude but opposite directions
A table-tennis ball is thrown at a stationary bowling ball. The table-tennis ball makes a one-dimensional elastic collision and bounces back along the same line. Compared with the bowling ball after the collision, the table-tennis ball has ____ - a same magnitude of momentum and the same kinetic energy. Consider a one-dimensional elastic collision between a moving object A and an object B initially at rest. How would you choose the mass of B, in comparison to the mass of A, in order that B should recoil with the greatest speed? - Particle A should be much more massive than particle B Stan argues that momentum cannot be conserved when a collision is not a head-on collision. Rachel insists it is conserved because each body receives an impulse of equal magnitude. Rachel is correct because - all of the above When the rate of burn and the exhaust velocity are constant, a rocket ascends with _______ - increasing acceleration The force that accelerates a rocket into outer space is exerted on the rocket by the ______ - exhaust gasses Two bodies with masses m1 and m2 are both moving east with velocities of magnitudes v1 and v2, where v1 is less than v2. The magnitude of the velocity of the center of mass of this system of two bodies is - greater than v1 and less than v2.
