Physics Midterm Review Unit 2
Picture of atwood machine* The system shown above is released from rest. If friction is negligible, the acceleration of the 4.0 kg block sliding on the table shown above is most nearly
A 0 B 1.7 m/s2 C 3.3 m/s2 D 5.0 m/s2 E 10.0 m/s2
On Earth, when a box slides across a horizontal board, the board exerts a frictional force of magnitude F0F0 on the box. The board and the box are moved to a planet with twice the radius but one-third the mass of Earth. When the box slides across the board, the frictional force exerted by the board on the box is now
A 1/12 F0 B 1/6 F0 C 2/3 F0 D F0
An object is moving to the west at a constant speed. Three forces are exerted on the object. One force is 10 N directed due north, and another is 10 N directed due west. What is the magnitude and direction of the third force if the object is to continue moving to the west at a constant speed?
A 10√3 N , directed northwest B 10√3 N , directed southeast C 10√2 N , directed northwest D 10√2 N , directed southeast
A 2kg object is released from rest near the surface of a planet such that its gravitational field is considered to be constant. The mass of the planet is unknown. The object's speed after falling for 3 s is 75 m/s. Air resistance is considered to be negligible. Calculate the weight of the 2kg object on the planet of unknown mass.
A 2N B 25N C 50N D 75N
An elevator carrying a person of mass m is moving upward and slowing down. How does the magnitude F of the force exerted on the person by the elevator floor compare with the magnitude mg of the gravitational force?
A F < mg B F = mg C F > mg D F can be greater than or less than mg, depending on the speed of the elevator.
Picture of 2 blocks in elevator* Box A of mass m sits on the floor of an elevator, with box B of mass 2m on top of it, as shown in the figure above. The elevator is moving upward and slowing down. FA is the magnitude of the force exerted on box A by box B, FB is the magnitude of the force exerted on box B by box A, and Fg is the magnitude of the gravitational force exerted on box B. Which of the following ranks the forces in order of increasing magnitude?
A FB = FA = Fg B (FB = FA) < Fg C FB < (FA = Fg) D Fg < FB < FA
A group of students attaches an object of unknown mass to a spring with unknown spring constant. The students displace the object from equilibrium and measure the period of oscillation of the object. The students' procedure could be used to determine which of the following? Select two answers.
A If the mass of the object were known, the students could use the procedure to determine the spring constant of the spring. B If the mass of the object were known, the students could use the procedure to determine the acceleration due to gravity. C If the spring constant were known, the students could use the procedure to determine the gravitational mass of the object. D If the spring constant were known, the students could use the procedure to determine the inertial mass of the object.
Picture of free body diagram* A block slides to the right on a rough horizontal surface. The forces exerted on the block are shown above. Which of the following statements about the frictional force Ff exerted on the block is true?
A It is the only force acting on the block that is caused by microscopic interactions. B It does not depend on the materials that the block and the surface are made of. C It is caused by gravitational interactions between the atoms in the block and the atoms in the surface. D It is the sum of all the microscopic contact forces between the bottom of the block and the surface.
Picture of incline plane with block with xy-axis on top right* A box of mass mm is released from rest and accelerates down a ramp that is at an angle θ to the horizontal, as shown. The coefficient of kinetic friction between the box and the ramp is μ. As the box is sliding down the ramp, how are the magnitudes of the horizontal and vertical components of the box's velocity changing, if at all?
A Not changing; Not changing B Not changing; Increasing C Increasing; Not changing D Increasing; Increasing
Picture of distance timeline* At time t = 0 two figure skaters are moving together over ice with negligible friction, as shown above. Skater 1, represented by the large black dot, is twice as massive as skater 2, represented by the gray dot. At t = 2 s the skaters push off of one another. The location of skater 1 is shown at t = 4 s . At t = 4 s , skater 2 is located at which of the labeled points?
A Point A B Point B C Point C D Point D
Picture of two blocks connected by string being pulled* Two identical blocks A and B are connected by a lightweight rope. Block A is pulled to the right by a constant force F0. The blocks are moving to the right across a rough surface and approach point P, where the rough surface transitions to a surface with negligible friction. How does the tension, T, in the rope connecting the blocks change, if at all, as block A passes point P?
A T decreases. B T increases. C T remains constant. D The change in T cannot be determined without knowing the coefficient of friction and the mass of the blocks.
When a box is at rest on a level floor, forces are exerted between the atoms in the bottom surface of the box and atoms in the top surface of the floor. Why does the floor not exert a frictional force on the box?
A The force exerted between any atom in the floor and any atom in the box is always vertical, leading to a normal force but not a frictional force. B The forces exerted between atoms are equal in magnitude and opposite in direction, so the net force between the box and floor is zero. C The horizontal component of the force exerted between any atom in the floor and any atom in the box is always negligible compared to the vertical component of the force. D The horizontal components of the forces exerted between atoms in the floor and atoms in the box are not negligible but sum to zero.
A block slides down an inclined plane in a classroom. Which of the following pieces of information are needed to determine whether the velocity of the block will be constant? Select two answers.
A The mass of the block B The angle of the inclined plane C The acceleration due to gravity in the classroom D The coefficient of kinetic friction between the block and the inclined plane
Picture of block on ramp* A block of mass m is at rest on a rough incline, as shown in the figure above. Which of the following forces must have a magnitude equal to mg? Select two answers.
A The total force exerted on the block by the incline B The normal force exerted on the block by the incline C The force of friction exerted on the block by the incline D The gravitational force exerted on Earth by the block
A vehicle lands on Mars and explores its surface. The average gravitational field on the surface of Mars is 3.7 N kg . The weight of the vehicle is defined as the gravitational force exerted on it. Which of the following statements are true about the vehicle's weight? Select two answers.
A The vehicle's weight was constant until it reached the surface of Mars. B The vehicle's weight increased while it was descending to the surface of Mars. C The vehicle's weight always equals the normal force exerted by Mars on the vehicle while it is landing. D The vehicle weighs less on the surface of Mars than on the surface of Earth.
2 pictures of atwood machine with carts* In Figure 1, cart Y is connected to cart X by a tight string and is also connected to the hanging block of mass m0m0 by a light string that passes over a pulley. Figure 2 shows a system that is identical except for one change: cart Y and X are connected by a spring at its equilibrium length. Both systems are released from rest. Is the hanging block's acceleration as a function of time the same in both systems, and why or why not?
A Yes, because the net external force exerted on both systems is the same. B Yes, because the tension in the string connecting the block to cart Y is determined by the masses of cart Y and the block. C No, because the net external force exerted on each system is different. D No, because the tension in the string connected to the block is constant in one system but not in the other.
Picture of atwood machine* Blocks A and B, of masses mA and mB, are at rest on a frictionless surface, as shown above, with block A fixed to the table. Block C of mass mC is suspended by a string that is tied to block B over an ideal pulley. Which of the following gives the magnitude of the force exerted by block A on block B ?
A mBg B mCg C mA mC/mA+mB D mB mCm/A+mB g
Picture of atwood machine* Blocks 1 and 2 are connected by a light string that passes over a pulley with negligible mass and friction, as shown in the figure. Block 1 is on a table covered with two different materials, A and B. The two-block system is released from rest, and the speed of block 1 begins to increase. When block 1 reaches material B, its speed increases at a greater rate. Which of the following correctly compares the coefficient of kinetic friction μμ between block 1 and the two materials and describes the change in the magnitude of the net force on block 2 as block 1 slides from material A to material B?
A μA>μB; Decreases B μA>μB; Increases C μA<μB; Increases D μA<μB; Decreases
Picture of two blocks next to each other* Two blocks of masses 1.0 kg and 2.0 kg, respectively, are pushed by a constant applied force F across a horizontal frictionless table with constant acceleration such that the blocks remain in contact with each other, as shown above. The 1.0 kg block pushes the 2.0 kg block with a force of 2.0 N. The acceleration of the two blocks is
A 0 B 1.0 m/s2 C 1.5 m/s2 D 2.0 m/s2 E 3.0 m/s2
Picture of rope connected to block* A rope of negligible mass supports a block that weighs 30 N, as shown above. The breaking strength of the rope is 50 N. The largest acceleration that can be given to the block by pulling up on it with the rope without breaking the rope is most nearly
A 6 m/s2 B 6.7 m/s2 C 10 m/s2 D 15 m/s2 E 16.7 m/s2
A toy doll and a toy robot are standing on a frictionless surface facing each other. The doll has a mass of 0.20 kg, and the robot has a mass of 0.30 kg. The robot pushes on the doll with a force of 0.30 N. The magnitude of the acceleration of the robot is
A zero B 0.60 m/s2 C 1.0 m/s2 D 1.5 m/s2
picture of girl pushing box* Two students need to move two identical boxes of mass M0 across a room where friction between the floor and the boxes cannot be neglected. One student moves the first box by pushing with a force of magnitude F0 at an angle θ from the horizontal, as shown in the figure for scenario 1. The other student moves the second box by pulling with a force of magnitude F0 at the same angle θ from the horizontal, as shown in the figure for scenario 2. Which of the following graphs could describe the motion of the two boxes as they are moved across the room?
scenario 2 dotted line linear up right; scenario 1 straight horizontal line y-intercept above 0