Physics Semester 1 Practice

Two spheres of mass M and 2M float in space in the absence of external gravitational forces, as shown in the figure. Which of the following predictions is correct about the motion of the center of mass of the two-sphere system?

The center of mass remains at rest.

The diagram above shows the forces exerted on an object. Which of the following dot diagrams best represents the position of the object at equal time intervals? (Fn(up)=Fg(down); F1(right)>F2(left))

* * * * * *

Two blocks are tied together with a string. They are thrown onto a layer of ice such that they spin around their center of mass C as they slide horizontally across the icy surface, as shown in the figure. A graph of the two-block system's velocity as a function of time is shown. Based on the graph, which of the following claims are correct about the system? Select two answers.

The acceleration of the center of mass of the system is constant. The system's acceleration vector is opposite to the direction of the system's velocity vector.

500 N up, 100 N left, 500 N down, F right The figure above shows the forces exerted on a block that is sliding on a rough horizontal surface: The weight of the block is 500 N, the normal force is 500 N, the frictional force is 100 N, and there is an unknown force F exerted to the right. The acceleration of the block is 0.4 m/s2. The value of F is most nearly

120 N

An object travels along a straight line across a horizontal surface, and its motion is described by the velocity versus time graph shown in the figure. (y=2x; x=0-x=5) Which of the following methods will determine the total displacement of the object between 0 s and 5 s? Select two answers.

Finding the area bound by the horizontal axis and the curve from 0 s to 5 s, Using Average Speed=total distance/total and multiplying the average speed of 5 ms by a total time of 5 s

Three identical blocks, X, Y, and Z, hang from identical strings, as shown in the figure. Which of the following free-body diagrams could represent the forces exerted on block Y?

Ftension (up) = Fgravity + Ftension (down)

Two blocks are connected by a rope, as shown above. The masses of the blocks are 5 kg for the upper block and 10 kg for the lower block. An upward applied force of magnitude F acts on the upper block. The system is moving and accelerating upward. A pair of scissors cuts the rope. Which of the following describes the motion of the 10 kg block immediately after the rope has been cut?

The block continues to move upward but begins to accelerate downward.

(Force, Magnitude) = (Fgrav, 10N), (Ffriction, 2N), (Fapp(horizontal), 8N), (Fnormal, 10N) The table shows experimental data of the magnitude of four forces exerted on a 2kg object as it slides across a horizontal surface. Which of the following could represent the magnitude of the net force that is exerted on the object? Select two answers.

6N, 10N

(Brick 1 is tiny sitting on Brick 2 which is huge. Forces acting on Brick 2 are F1 down, Fg down, and Fn up) Two bricks are stacked on a floor. A student draws the force diagram for brick 2, as shown above. The forces are an upward normal force, a downward force exerted by brick 1, and a downward gravitational force. How many of the forces, if any, in the force diagram are contact forces caused by microscopic interactions?

Only 2

A student is provided with a battery-powered toy car that the manufacturer claims will always operate at a constant speed. The student must design an experiment in order to test the validity of the claim. Which of the following measuring tools can the student use to test the validity of the claim? Select two answers.

Photogates placed at the beginning, end, and at various locations along the track that the car travels on, A meterstick to measure the distance of the track that the car travels on

A student wants to study the motion of an object that has a constant acceleration. Which of the following experiments could the student conduct to provide the best situations in which an object has a constant acceleration? Select two answers.

Release a ball from rest near Earth's surface, Release a cart from rest such that it travels down an incline of 40°40° with respect to the ground

A student wants to investigate the motion of a ball by conducting two different experiments, as shown in Figure 1 and Figure 2 above. In Experiment 1, the student releases a ball from rest and uses a slow-motion camera to film the ball as it falls to the ground. Using video analysis, the student is able to plot the ball's horizontal position x and vertical position y as a function of time t. In Experiment 2, the student horizontally rolls the same ball off a table, and uses video analysis to plot the ball's horizontal position x and vertical position y as a function of time t starting from the instant the ball leaves the table. The graphs from each experiment are shown above along with each graph's best-fit curve line. Which of the following conclusions can the student draw from the graphs, and why?

Since the balls have the same vertical position at any given time, they reach the ground at the same time.

A book is at rest on the top of a table. A student makes the following claim: "An attractive electromagnetic force is exerted on the book from the table, and this force can also be classified as the normal force." Which of the following statements correctly justifies the student's claim?

The claim is incorrect because the charged particles of the table exert an upward repulsive force on the charged particles of the book.

An object travels down a ramp at a constant acceleration. The object experiences a force of friction and a gravitational force. Which of the following could be true about the motion of the object? Select two answers.

The force of friction between the surface and the object is less than the component of the gravitational force that is parallel to the ramp; If the object increased in mass, the object's acceleration would change.

A tennis ball is thrown against a vertical concrete wall that is fixed to the ground. The ball bounces off the wall. How does the force exerted by the ball on the wall compare with the force exerted by the wall on the ball?

The forces exerted by the ball and the wall have the same magnitude

An object is sliding to the right along a straight line on a horizontal surface. The graph shows the object's velocity as a function of time. What is the object's displacement during the time depicted in the graph? (Y=-0.5x+4, 0<X<8)

0m

An Atwood machine is set up by suspending two blocks connected by a string of negligible mass over a pulley, as shown in the figure above. The pulley has negligible mass but there is friction as it rotates. The system is released from rest, and after 1.0 s the speed of the 3 kg block is 1.8 m/s. Which of the following is the best estimate of the external frictional force acting on the two-block system? (Blocks are 2kg and 3kg)

1.0 N

The free body diagram shown above is for a 5 kg box on a rough surface being pulled to the right at a constant speed by a string that is at an angle of 30° above the horizontal. The coefficient of kinetic friction between the box and the surface is 0.30. The tension in this string is most nearly

14.47 N

An Atwood's machine is set up by suspending two blocks connected by a string of negligible mass over a pulley, as shown above (3kg and 2kg). The blocks are initially held at rest and then released at time t0=0 s. The speed of the 3 kg block at time t1=2.0 s is most nearly

4.0 m/s

. . . . . . . . . . . . . . . A student performs an experiment in which the horizontal position of a toy car is recorded on ticker tape from a device that places dots on the tape in equal time intervals. The series of dots in the figure represents the motion of an object moving from the negative direction to the positive direction along the horizontal direction. The time interval between each recorded dot is 1s. Which of the following experiments could the student have conducted to create the data shown on the ticker tape?

A toy car that initially increases its speed, travels at a constant speed, and then decreases its speed.

A student wants to launch a toy dart toward a target that hangs from a light string. At time t=0, the dart is launched with an initial speed v0 at an angle θ0 above the horizontal ground. At the instant the dart is launched, the string is cut such that the target begins to fall straight down. The positive horizontal direction is considered to be to the right, and the positive vertical direction is considered to be up. Which of the following graphs could represent the vertical component of the velocity as a function of time for the dart and the target immediately after the dart is launched and the target begins to fall?

Dart: above x-axis, decreasing; Target: below x-axis, decreasing

An object slides across a horizontal surface such that it slows down due to the force of friction that is exerted on the object. The object and the direction of its displacement are shown in the figure. Which of the following free-body diagrams could represent the forces that are exerted on the object?

Fnormal up = Fgravity down; Ffriction to the left (smaller than both)

A potato falling vertically downward is struck by a dart that is traveling vertically upward, as shown above. The dart and potato then collide, stick together, and continue moving after the collision. Consider the dart-potato system. Which of the following graphs best represents the speed v of the center-of-mass of the dart-potato system, as a function of time t, before, during, and after the collision?

Line with a constant slope increasing

An astronaut in deep space is at rest relative to a nearby space station. The astronaut needs to return to the space station. A student makes the following claim: "The astronaut should position her feet pointing away from the space station. Then, she should repeatedly move her feet in the opposite direction to each other. This action will propel the astronaut toward the space station." Is the student's claim correct? Justify your selection.

No. The astronaut's feet are not exerting a force on another object, so there is no external force to accelerate the astronaut toward the space station.

Three blocks are connected by strings and pulled to the right by a force with magnitude F0, as shown in the figure above. All frictional forces are negligible. The tension in the right and left strings have magnitudes T1 and T2, respectively. Taking the positive direction to be toward the right, which of the following is a correct equation of motion for the block of mass m2? (m3-T2-m2-T1-m1-F0)

T1 - T2 = m2a

Gravitational Force of Object A on Object B = 2.7×10−10N Gravitational Force of Object B on Object A = 2.7×10−10N Object A of mass 2kg is gravitationally attracted to object B of mass 2kg as the two objects float in space. Frictional forces are negligible. The gravitational forces of attraction between the two objects are shown in the table above. Which of these claims about the motion of the center of mass of the two-object system is true?

The center of mass will not accelerate.

A student uses both hands to push a door such that it moves and swings open after the force has been applied. The student then makes the following claim: "I can use both of my hands to apply a constant force on my body so that my body falls backward." Which of the following statements correctly justifies the student's claim?

The claim is not correct because the student's body will exert a force of equal magnitude back on the student's hands as a result of Newton's third law of motion.

Two identical books are stacked on a table. A third identical book is then placed on top of the first two, causing an increase in the normal force exerted by the bottom book on the middle book. Which of the following is a correct explanation for the increase in this normal force?

The third book produces an additional downward force on the middle book, thus increasing the upward force exerted by the bottom book to maintain equilibrium.

In one experiment, a student rolls a 2 kg ball such that it collides with a wall with a force of 10,000 N. In a second experiment, the student rolls a 5 kg ball such that it collides with the wall at a force of 5000 N. In both experiments, the balls bounce back from the wall and eventually come to rest. Which of the following statements is true regarding the force that the wall exerts on each ball?

The wall exerts a greater force on the 2 kg ball than on the 5 kg ball since the force from the wall on each ball is equal to the force that each ball exerts on the wall.

An object undergoes an acceleration as it travels along a straight, horizontal section of a track. Which of the following graphs could represent the motion of the object? Select two answers

X-Axis: Time squared & Y-Axis: Position; X-Axis: Time & Y-Axis: Speed

Identical objects, object X and object Y, are tied together by a string and placed at rest on an incline, as shown in the graph. The string has a length of 2 m. The system of the two objects is released from rest, and a graph of the velocity of the center of mass of the system as a function of time is shown in the figure. If the string was cut and object Y was released from rest while object X was held at rest, which of the following claims is correct about the new acceleration of the center of mass of system anew compared to the original acceleration of the center of mass of the system aoriginal ?

anew will be less than aoriginal

Two students wish to determine the value of g, the acceleration due to gravity at Earth's surface. The students have a collection of blocks of different masses, a string of negligible mass, a pulley of negligible mass, and a device for measuring acceleration. The students attach two of the blocks to the ends of the string and pass the string over the pulley so the blocks hang vertically on either side. The blocks are then released from rest, and their acceleration is measured. The students' data for one trial are shown below, with m1 and m2 equal to the masses of the blocks. Considering the gravitational forces acting on the blocks, do the data provide a reasonable determination of the value of g, and what is a possible justification for why or why not? (M1(g)=400; M2(g)=600; a(m/s^2)=1.0)

No, because the calculated value of g is too small, possibly due to an additional force exerted on the blocks-string system.

Two blocks are connected by a rope, as shown above. The masses of the blocks are 5 kg for the upper block and 10 kg for the lower block. An upward applied force of magnitude F acts on the upper block. If the net acceleration is downward but has a magnitude less than g, then which has the larger magnitude, the force F or the tension in the rope?

Force F

An object is released from rest near a planet's surface. A graph of the acceleration as a function of time for the object is shown for the 4 s after the object is released (constant acceleration of -5m/s^2 for 4 s). The positive direction is considered to be upward. What is the displacement of the object after 2 s?

-10 m

At time t=0, a moving cart on a horizontal track is at position 0.5m. Using a motion detector, students generate a graph of the cart's velocity as a function of time, as shown above. At t=2.5s, the cart's position is most nearly (Y=-2X+3)

1.75m

A ball is released from rest from the twentieth floor of a building. After 1 s, the ball has fallen one floor such that it is directly outside the nineteenth-floor window. The floors are evenly spaced. Assume air resistance is negligible. What is the number of floors the ball would fall in 3s after it is released from the twentieth floor?

7 to 10 floors

Given the net forces on and the masses of the blocks shown above, which two blocks have the same acceleration? Select two answers. (Block A (5kg) = 20N; Block B (10kg) = 25N; Block C (20kg) = 100N; Block D (20kg) = 80N)

Block A; Block D

(B=2M)-(F2)-(A=M)-(F1) Blocks A and B, of masses m and 2m, respectively, are connected by a light string and pulled across a surface of negligible friction with a constant force F1, as shown above. The acceleration of the blocks is a. The force of the string pulling block B forward has magnitude F2. Which of the following claims correctly describes the relationship between the magnitude of the forces acting on the blocks?

F1 is greater than F2

The system shown above consists of two identical blocks that are suspended using four cords, each of a different length (30-60-90 Triangle of Cord 2, Cord 1, and ceiling with cord 3 connecting to a block and cord 4 extending from there to another block (both blocks of mass M)). Which of the following claims are true about the magnitudes of the tensions in the cords? Select two answers.

T1cos30°=T2cos60°; T1+T2=T3

A potato falling vertically downward is struck by a dart that is traveling vertically upward, as shown above. The dart and potato then collide, stick together, and continue moving after the collision. The weight of the dart is W. Which of the following claims best describes the magnitude of the net force on the dart immediately before, during, and immediately after the collision with the potato?

It is equal to W just before the collision, greater than W during the collision, and equal to W again after the collision.

Two students want to determine the speed at which a ball is released when thrown vertically upward into the air. One student throws the ball into the air while the other student measures the total time that the ball is in the air. The students use a meterstick to measure the release height of the ball. Which of the following equations should the students use to determine the speed at which the ball was released?

Use y=y0+vy0t+12ayt2 from the moment in time in which the ball was released to the moment in time in which the ball hits the ground.

Block X of mass M is attached to block Y of mass 2M by a light string that passes over a pulley of negligible friction and mass, as shown above. In which direction will the center of mass (COM) of the two-block system move after it is released from rest, and what is the magnitude of the acceleration a of block X ?

down and to the right; 2g/3

A car initially at rest accelerates at 10m/s^2. The car's speed after it has traveled 25 meters is most nearly

22.0 m/s

A student predicts that a block sliding down a ramp inclined at 45 degrees should have an acceleration of approximately 7 m/s2. The block is released from rest, and the student measures the distance the block travels and the time it takes to travel that distance. The student determines that the block's acceleration is only 5.5 m/s2. Which of the following is the most likely reason for the difference between the predicted and calculated accelerations?

The student's model used to make the prediction did not account for all of the forces that are exerted on the block.

A cart with an unknown mass is at rest on one side of a track. A student must find the mass of the cart by using Newton's second law. The student attaches a force probe to the cart and pulls it while keeping the force constant. A motion detector rests on the opposite end of the track to record the acceleration of the cart as it is pulled. The student uses the measured force and acceleration values and determines that the cart's mass is 0.4kg. When placed on a balance, the cart's mass is found to be 0.5kg. Which of the following could explain the difference in mass?

The track was not level and was tilted slightly downward

Two blocks, with masses indicated in the figure above (m & 2m), are at rest on a horizontal surface and connected by a string of negligible mass and a compressed spring. There is negligible friction between the blocks and the surface. The string is cut, and the spring pushes the blocks away from each other. Which of the following statements are true about the motion of the blocks immediately after the string is cut? Select two answers.

The velocity of the center of mass of the two-block system is zero; The magnitude of the acceleration of the left block is greater than that of the right block.

(Total #, Distance, Force Friction) = (1, 0.2, 0.6), (2, 0.5, 1.5), (3, 0.7, 2.1) An object rotates at various distances from the center of a disk such that the object experiences a force of friction from the disk. Data collected from the experiment are shown in the table above. Each location of the disk rotates such that the tangential speed at that point remains constant. What is the magnitude of the force of friction exerted on the object if its mass is doubled and it is placed at a distance of 0.6 m from the disk's center?

3.6 N

Force Label, Magnitude: (Fapp, 28N), (Ffriction, 4N), (Fgrav, 20N), (Fnormal, 20N) A 2kg object is initially at rest at time t=0s. It then slides across a rough, horizontal surface under the influence of only the four forces shown in the table above. What is the speed of the object at time t=3s ?

36 m/s

A student wants to investigate the motion of a ball by conducting two different experiments, as shown in Figure 1 and Figure 2 above. In Experiment 1, the student releases a ball from rest and uses a slow-motion camera to film the ball as it falls to the ground. Using video analysis, the student is able to plot the ball's horizontal position x and vertical position y as a function of time t. In Experiment 2, the student horizontally rolls the same ball off a table, and uses video analysis to plot the ball's horizontal position x and vertical position y as a function of time t starting from the instant the ball leaves the table. The graphs from each experiment are shown above along with each graph's best-fit curve line. In Experiment 1, what is the speed of the ball the instant it makes contact with the ground?

5.4 m/s

Object 1 and object 2 travel across a horizontal surface, and their horizontal velocity as a function of time is shown in the graph. (Object 1: y=-10x+40, Object 2: y=10x) Which of the following statements is correct about the two-object system?

After 2s , object 1 travels a greater distance than object 2 travels.

A student wants to launch a toy dart toward a target that hangs from a light string. At time t=0, the dart is launched with an initial speed v0 at an angle θ0 above the horizontal ground. At the instant the dart is launched, the string is cut such that the target begins to fall straight down. The positive horizontal direction is considered to be to the right, and the positive vertical direction is considered to be up. Figure 1 shows a displacement-versus-time graph for the dart. Figure 2 shows a displacement-versus-time graph for the target. For both graphs, the component of the displacement is not indicated. Which displacement component, horizontal or vertical, is represented by the graph for each object?

Dart: vertical, Target: vertical

Students work together during an experiment about Newton's laws. The students use a setup that consists of a cart of known mass connected to one end of a string that is looped over a pulley of negligible friction, with its other end connected to a hanging mass. The cart is initially at rest on a horizontal surface and rolls without slipping when released. The inertia of the cart's wheels is negligible. Students have access to common laboratory equipment to make measurements of components of the system. Students take measurements of the force F0 , directed to the left, needed to hold the cart in place as well as the tension FT in the horizontal section of string. The students take three measurements for each force. Which of the following sets of measurements would provide the most precise determination of the correct relationship between the net force and the vector sum of the individual forces exerted on the cart?

F0(N) = 4.0, 4.7, 4.8 FT(N) = 4.02, 4.65, 4.77

A motion sensor is used to create the graph of a student's horizontal velocity as a function of time as the student moves toward and away from the sensor, as shown above. The positive direction is defined as the direction away from the sensor. Which of the following describes the student's final position xf in relation to the starting position x0 and the student's average horizontal acceleration ax between 0.0 s and 3.0s? (Graph starts (0,0), moves linearly to (0.5, 1.0), then constant to (1.25,1.0), decreasing to (1.5,0), constant to (2.0,0), decreasing to (-.5, 2.25), constant to (3.0,-.5), increasing to (3.25,0), constant to (4,0), then ends)

Position xf is farther away from the sensor than x0, and ax is negative. (**The graph shows 0s-4s, but you only need 0s-3s**)

Two blocks are connected by a rope, as shown above. The masses of the blocks are 5 kg for the upper block and 10 kg for the lower block. An upward applied force of magnitude F acts on the upper block. If F=300 N, which of the following predictions about the acceleration of the two-block system is correct?

The acceleration is upward with a magnitude of g

A ladybug is crawling up a wall at constant speed, as shown above. Which of the following are correct justifications for how forces help the ladybug move up the wall? Select two answers.

The ladybug exerts a downward force on the wall to move itself up the wall; The upward force of the wall on the ladybug moves the ladybug up the wall

A ball is dropped onto the floor and bounces upward. Which of the following claims are correct about the force that the ball exerts on the floor compared to the force that the floor exerts on the ball when the ball and the floor are in contact?

The magnitude of the forces exerted by both objects is the same because the ball and the floor cannot exert forces of different magnitudes on each other.

Students work together during an experiment about Newton's laws. The students use a setup that consists of a cart of known mass connected to one end of a string that is looped over a pulley of negligible friction, with its other end connected to a hanging mass. The cart is initially at rest on a horizontal surface and rolls without slipping when released. The inertia of the cart's wheels is negligible. Students have access to common laboratory equipment to make measurements of components of the system. The students double the mass that hangs from the string. They also replace the original cart with a new cart that has double the mass. By doubling both masses, how will the tension in the string and the acceleration of the cart change?

The tension will double, but the acceleration will stay the same.

The force diagram above shows a box accelerating to the right on a horizontal surface of negligible friction. The tension T is exerted at an angle of 30° above the horizontal. If μ is the coefficient of kinetic friction between the box and the surface, which of the following is a correct mathematical equation derived by applying Newton's second law to the box?

a=(Tcosθ - μ(Mg-Tsinθ))/M

A block is moving horizontally with a speed of v0 when it encounters a ramp, as shown above. Which of the following graphs best represents the position of the block measured from the top of the ramp as a function of time if friction is negligible?

positive increasing curve (increasing concave up, min at origin, looks like 1/2 a parabola)

A block of mass m1 collides with a block of mass m2 such that block of mass m1 becomes at rest while block of mass m2 slides across a surface of negligible as it travels with a constant speed toward the frictional surface, as shown above. The coefficient of kinetic friction between block of mass m2 and the frictional surface is μk. What is the rate of change of the speed of the center of mass of the two-block system after the block of mass m2 enters the frictional surface?

uk*m2*g/(m1+m2)

A bowling pin is thrown vertically upward such that it rotates as it moves through the air, as shown in the figure. Initially, the center of mass of the bowling pin is moving upward with a speed vi of 10 ms. The maximum height of the center of mass of the bowling pin is most nearly...

vi^2/2g

An object is dropped from the top of a building near Earth's surface. After 2 s, a second identical object is dropped from the same building from the same height. After 4 s, the first object strikes the ground. The graph shows the speeds ν of both objects as a function of time t. What is the approximate acceleration of the center of mass of the two-object system at the moment right before the first object reaches the ground? (Object 1: y=10x (0<X<4) and Object 2: y=10x (2<X<4))

10 m/s^2

A block is pulled along a surface of negligible friction by a spring scale that exerts a force F on the block. The mass of the block is 4kg, and the spring scale reads 10N. Which of the following free-body diagrams can be used to show the magnitude and direction of all the forces exerted on the block as it is pulled along the surface?

Fnormal up (4 blocks) = Fgravity down (4 blocks); Fspring = right (1 block)

A student wants to investigate the motion of a ball by conducting two different experiments, as shown in Figure 1 and Figure 2 above. In Experiment 1, the student releases a ball from rest and uses a slow-motion camera to film the ball as it falls to the ground. Using video analysis, the student is able to plot the ball's horizontal position x and vertical position y as a function of time t. In Experiment 2, the student horizontally rolls the same ball off a table, and uses video analysis to plot the ball's horizontal position x and vertical position y as a function of time t starting from the instant the ball leaves the table. The graphs from each experiment are shown above along with each graph's best-fit curve line. Suppose that Experiment 1 and Experiment 2 are conducted at the same time; one student drops the ball from rest at the same instant that a second student horizontally rolls an identical off the table. After both balls have traveled half their vertical distance to the floor, what is the acceleration of the center of mass of the two-ball system relative to Earth?

Equal to g

Object X and object Y are at rest on a horizontal surface. Object X is in contact with object Y. The force diagrams for both objects are shown above. (Object 1 has F1 up, F2 down, and F3 left; Object Y has F4 up, F5 down, and F6 right) Which two forces make up an action-reaction pair?

F3 and F6 , because both forces are exerted on different objects, have the same magnitude, and are in opposite directions.

The diagram above represents the forces exerted on a box that a child is holding. FN represents the force applied by the child's hand, and Fg represents the weight of the box. The child begins to raise the box with increasing speed. Which of the following claims is correct about force Fh that is exerted by the box on the child's hand as the box is being raised?

Fh=FN , where FN is larger as the box is being raised than when it was being held

A student wants to launch a toy dart toward a target that hangs from a light string. At time t=0, the dart is launched with an initial speed v0 at an angle θ0 above the horizontal ground. At the instant the dart is launched, the string is cut such that the target begins to fall straight down. The positive horizontal direction is considered to be to the right, and the positive vertical direction is considered to be up. A student makes the necessary measurements to create the graph shown, which represents the vertical component of the velocity as a function of time for the dart and for the target from t=0 until the instant the dart hits the target. At t=0, the target is a vertical distance h above the dart. The curves for the dart and the target each have the same area between them and the horizontal axis. Both curves also have the same slope. Which of the following is the best method to determine the distance h from the graph?

Find twice the area under the curve for the dart's data.

A stick is used to hit a ball at an angle above the horizontal, as shown in Figure 1. Figure 2 shows the free body diagram of the ball. Figure 3 shows the free body diagram of the stick. Which of the following pairs of forces represents an action-reaction pair and the object or objects involved in the action-reaction pair? (Ball - up to left: Fstick = 15N; down: Fgravity = 5N;; Stick: down to right: Fball = 15N; Fgravity = 10N)

Fstick and Fball

A student must determine the relationship between the inertial mass of an object, the net force exerted on the object, and the object's acceleration. The student uses the following procedure. The object is known to have an inertial mass of 1.0kg. Step 1: Place the object on a horizontal surface such that frictional forces can be considered to be negligible. Step 2: Attach a force probe to the object. Step 3: Hang a motion detector above the object so that the front of the motion detector is pointed toward the object and is perpendicular to the direction that the object can travel along the surface. Step 4: Use the force probe to pull the object across the horizontal surface with a constant force as the force probe measures force exerted on the object. At the same time, use the motion detector to record the velocity of the object as a function of time. Step 5: Repeat the experiment so that the object is pulled with a different constant force. Can the student determine the relationship using this experimental procedure?

No, because the motion detector should be oriented so that the object moves parallel to the line along which the front of the motion detector is aimed.

A student must design an experiment to determine the relationship between the mass of an object and the resulting acceleration when the object is under the influence of a net force. Which of the following experiments should the student conduct in order to determine the relationship between all three quantities?

Slide an object of known mass across a rough surface, using a constant applied force that can be measured by a force sensor. Place a motion detector behind the object so that its speed can be measured as it slides across the surface. Repeat the experiment for different applied forces.

(M-3M) A block of mass M and a block of mass 3M are connected by a string, as shown above. The blocks are held with the string horizontally and are released from rest at the same time from a height H above the ground. How does the acceleration of the center of mass of the system compare to the acceleration of the object of mass M ?

The acceleration of the center of mass is the same as the acceleration of the object of mass M .

A student is tasked with using a force table to balance a small ring in the center of a pin, as shown in Figure 1. For each of the four strings shown, one end is attached to the small ring, and the other end is attached to a hanger that can hold masses. Each string is wrapped around a pulley so that the hanger and masses are at rest. The location of each pulley may be changed. Figure 2 shows a top-down view of the free-body diagram of the forces exerted on the pin at a particular moment in time (Up: 3N; Down: 1N; Left: 8N; Right: 5N). From a top-down perspective, in what direction will the pin accelerate?

Up and to the left

A student drops a rock from the top of a cliff such that the rock falls downward toward Earth's surface in the absence of air resistance. The downward direction is considered to be the positive direction. The graph shows the rock's velocity as a function of time. Which of the following methods should be used to determine the total distance traveled by the rock after 4s ? (Y=10x)

Use the area under the curve, as it states that the rock traveled 80 meters in total