Physics Semester 1 Practice
A cart of mass m is moving with speed v on a smooth track when it encounters a vertical loop of radius R, as shown above. The cart moves along the inside of the entire loop without leaving the track. All frictional forces are negligible.
The net force exerted on the cart must be equal to or greater than the weight of the cart.
A student throws a rock horizontally from the edge of a cliff that is 20 m high. The rock has an initial speed of 10 m/s. If air resistance is negligible, the distance from the base of the cliff to where the rock hits the level ground below the cliff is most nearly
20 m
A car initially at rest accelerates at 10 m/s^2. The car's speed after it has traveled 25 meters is most nearly
22.0 m/s
A car initially at rest accelerates at 10ms2. The car's speed after it has traveled 25 meters is most nearly
22.0 m/s
Force due to gravity 10N Force of friction 2N Horizontal applied force 8N Normal force 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
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
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. 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.
An object is released from rest near the surface of a planet. The vertical position of the object as a function of time is shown in the graph. All frictional forces are considered to be negligible. The strength of the gravitational field is most nearly
6 N/kg
A student wants to investigate uniform circular motion for an object in an amusement park ride. The student will ride inside of a hollow cylindrical tube that pins the student to the inside wall of the tube as it spins. As the tube spins, the bottom of tube is removed such that the tube becomes open at the top and bottom. At the instant shown in figure 1, the student is pinned against the right side of the tube. A diagram showing the forces exerted on the student is shown in figure 2. When the ride is finished, the student safely falls onto the padded cushions below the floor of the tube. Which of the following represents the magnitude of the force that the student exerts on the right side of the tube?
FNormal, because the force that the student exerts on the right side of the tube is an action-reaction pair with the normal force that the tube exerts on the student.
The figure above shows the position of a moon that orbits a planet in an elliptical path. Two specific locations of the moon, position A and position B, are labeled. As the moon orbits the planet from position A to position B, is the magnitude of the planet's force due to gravity exerted on the moon constant? Why or why not?
No, because the moon's distance from the planet is always changing.
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 θ0θ0 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?
D) (dart above the x axis, decreasing steadily and constant)(target below the x axis, decreasing steadily and constant)
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 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.
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.
An object attached to one end of a string moves in a circle at constant speed. Which of the following is correct?
The object is accelerating as it moves.
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.
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.
A student spins a cup that is in contact with a platform in a horizontal circular path at a constant speed, as shown in Figure 1. The platform is connected to two strings that are held by the student as the platform-cup system experiences uniform circular motion. A free-body diagram of the cup is shown in Figure 2. Which statement of reasoning best supports and correctly identifies the magnitude of the force the cup exerts on the platform?
√F1^2+F2^2, because this force represents the magnitude of the total force exerted on the platform by the cup.
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
120N
An object is released from rest near the surface of a planet. The velocity of the object as a function of time is expressed in the following equation. vy=(−3 ms2)t All frictional forces are considered to be negligible. What distance does the object fall 10 s after it is released from rest?
150 m
An object is dropped near the surface of a planet such that the gravitational field at the object's location is 8 N/kg. If the object is thrown upward at a speed of 20 m/s, what is the position of the object in relation to the position in which the object was released and thrown upward after 3s ?
24 m above the release position
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 ? FApplied28 FFriction4 FGravity20 FNormal20
36 m/s
FApplied28 FFriction4 FGravity20 FNormal20 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 ?
36m/s
A 10kg object is near a planet's surface such that the gravitational field strength is 4N/kg. With what force is the planet attracted to the 10kg object?
40N
A ball that is attached to a string travels in a horizontal, circular path, as shown in Figure 1. At time t0, the ball has a speed v0. The forces exerted on the ball at t0 are represented by the free-body diagram, as shown in Figure 2. At a later time t1, the tangential speed of the ball is increased to 2v0. What is the magnitude of the force that the ball exerts on the string at time t1?
4FTension
An object is thrown with a horizontal velocity of 20 m/s from a cliff that is 125 m above level ground. If air resistance is negligible, the time that it takes the object to fall to the ground from the cliff is most nearly
5 s
The graph above represents position x versus time t for an object being acted on by a constant force. The average speed during the interval between 1 s and 2 s is most nearly
6 m/s
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.
A) speed over time steadily increasing starting at middle & C) position over time squared steadily increasing starting at middle
A person throws a marble straight up into the air, releasing it a short height above the ground and catching it at that same height. If air resistance is negligible, which of the following graphs of position y versus time t is correct for the motion of the marble as it goes up and then comes down?
B) (curve like a rainbow; upside down u)
0 0.0 1 −4.9 2 −10.2 3 −15.6 4 −19.7 5 −24.4 6 −30.9 An astronaut performs an experiment near the surface of a moon by releasing an object at rest above a motion detector such that data can be collected about the object's vertical velocity as a function of time. The data are provided in the table. Which of the following graphs most likely represents the shape of the curve of the magnitude of the gravitational field strength near the surface of the moon as a function of time?
B) Constant straight line from left to right, no change in slope
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 & Block D
A planet travels in an elliptical orbit around its star, as shown above. Which arrow best shows the direction of the net force exerted on the planet?
C
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?
C) Normal force up(max block), Gravity force down(max block, Spring force right (one block)
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.
D) (Dart above x axis, angled constant line down)( Target below x axis, angles constant line down)
During an experiment, a block of mass M=0.20kg is placed on a disk that rotates about an axle through its center, as shown in the diagram. The block is moved to different distances R from the axle, and the tangential speed of the block is gradually increased until the mass begins to slip. The distance and maximum tangential speed before slipping, vmax, are recorded. A student creates a graph of vmax2 as a function of R, as shown. How should the student use the graph to most accurately determine the experimental value of the coefficient of static friction μS between the block and the disk?
Determine the slope of the best fit line and set it equal to μSg.
A student builds the apparatus shown. One end of a light string is attached to an object of mass m0, and the other end of the string is passed through a tube and attached to a second object of mass M. The student holds on to the tube and swings the object of mass m0 in a horizontal circle while the object of mass M remains at a constant height. The time it takes for the object of mass m0 to travel around its circular path is T. Which of the following options represents the essential measuring devices needed by the student to collect the necessary data to experimentally determine the gravitational field strength of the object of mass m0 due to Earth's gravitational field?
Mass balance, meterstick, and timer
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 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 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?
Position xf is farther away from the sensor than x0, and ax is negative.
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° with respect to the ground.
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.
A planet has two moons, Moon A and Moon B, that orbit at different distances from the planet's center, as shown. Astronomers collect data regarding the planet, the two moons, and their obits. The astronomers are able to estimate the planet's radius and mass. What additional information is needed to determine the time required for one of the moons to make one complete revolution around the planet?
The distance between the center of each moon and the planet.
A space station has a mass M and orbits Earth in a circular orbit at a height above Earth's surface. An astronaut in the space station appears weightless because the astronaut seems to float. Which of the following claims is true about the force exerted on the astronaut by Earth?
The force exerted on the astronaut by Earth is equal to the force exerted on Earth by the astronaut.
A planet travels in an elliptical path around a star, as shown in the figure. As the planet gets closer to the star, the gravitational force that the star exerts on the planet increases. Which statement of reasoning best supports and correctly identifies what happens to the magnitude of the force that the planet exerts on the star as the planet gets closer to the star?
The force increases because it is part of a Newton's third law pair of forces with the force that the star exerts on the planet.
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.
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.
The figure above shows the position of a moon that orbits a planet in an elliptical path. Two specific locations of the moon, position A and position B, are labeled. In what direction is the net force exerted on the moon?
Toward the planet
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. 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 ?
Use the area under the curve, as it states that the rock traveled 80 meters in total.
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?
close in the beginning, gradually become farther and father apart as time goes on
A ball of mass M swings in a horizontal circle at the end of a string of radius R at a constant tangential speed v0. A student gradually pulls the string inward such that the radius of the circle decreases while keeping the tangential speed v0 of the ball constant, as shown above. Which of the following graphs best represents the acceleration a of the ball as a function of time t?
curve up exponentially (flatter to more verticle)
An object is thrown with an initial speed v near the surface of Earth. Assume that air resistance is negligible and the gravitational field is constant. If the object is thrown vertically upward, the direction and magnitude of its acceleration while it is in the air is
downward and constant
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
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?
smaller initially then gets bigger and father apart as time goes on
An object is spun in a horizontal circle such that it has a constant tangential speed at all points along its circular path of constant radius. A graph of the magnitude of the object's tangential speed as a function of time is shown in the graph. Which of the following graphs could show the magnitude of the object's centripetal acceleration as a function of time?
straight constant line from left to right with no slope at 9m/s^2
A group of students prepare for a robotic competition and build a robot that can launch large spheres of mass M in the horizontal direction with a variable speed and from a variable vertical position and a fixed horizontal position x=0. The robot is calibrated by adjusting the speed at which the sphere is launched and the height of the robot's sphere launcher. Depending on where the spheres land on the ground, students earn points based on the accuracy of the robot. The robot is calibrated so that when the spheres are launched from a vertical position y=H and speed v0, they consistently land on the ground on a target that is at a position x=D. Positive directions for vector quantities are indicated in the figure. When the students arrive at the competition, it is determined that the height of the sphere launcher can no longer be adjusted due to a mechanical malfunction. Therefore, the spheres must be launched at a vertical position of y=H2. However, the spheres may be launched at speed v0 or 2v0. (b) In a clear, coherent paragraph-length response that may also contain diagrams and/or equations, describe the speed at which a sphere should be launched so that the students earn the maximum number of points in the competition.
1 point is earned for a statement that indicates that a sphere launched from a vertical height of y=H2 will result in a free fall time that is less than T . 1 point is earned for a statement that indicates that if the sphere is launched at the original speed v0 that the distance the sphere travels before hitting the ground will be x<D . 1 point is earned for a statement that indicates that with a launch height of y=H2 , and a speed of either v0 or 2v0 1 point is earned for a statement that indicates that to get the most points, since the students can no longer hit the target, they should aim for the 3-point zone by making 1 point is earned for a logical, relevant and internally consistent argument that addresses the required arguments or question asked and follows the guidelines described in the published requirements for the paragraph-length response.
A group of students prepare for a robotic competition and build a robot that can launch large spheres of mass M in the horizontal direction with a variable speed and from a variable vertical position and a fixed horizontal position x=0. The robot is calibrated by adjusting the speed at which the sphere is launched and the height of the robot's sphere launcher. Depending on where the spheres land on the ground, students earn points based on the accuracy of the robot. The robot is calibrated so that when the spheres are launched from a vertical position y=H and speed v0, they consistently land on the ground on a target that is at a position x=D. Positive directions for vector quantities are indicated in the figure. (a) On the axes below, sketch the graphs of the horizontal and vertical components of the sphere's velocity v as a function of time t between t=0, when the sphere is launched and t=T, when the sphere hits the target. Label t=T for the horizontal component of the sphere's velocity and the vertical component of the sphere's velocity.
1 point is earned for sketching a horizontal line above the horizontal axis from t=0 to t= T 1 point is earned for sketching a line with a constant slope that begins at the origin and becomes more negative from t= 0 to t= T (straight, steady line down)
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
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 xx 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
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 cart is constrained to move along a straight line. A varying net force along the direction of motion is exerted on the cart. The cart's velocity v as a function of time t is shown in the graph above. The five labeled points divide the graph into four sections. For which segment does the cart move the greatest distance?
AB (curve like rainbow)
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 θ0θ0 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
A student is riding a Ferris wheel that moves at a constant tangential speed around a vertical circular path of radius R, as shown in Figure 1. The student is sitting on a scale. At the instant the moving student is located at point P, the scale exerts a force of magnitude FScale on the student and Earth exerts a force of magnitude FGravity on the student, as shown in the free-body diagram in Figure 2. Which of the following statements provides reasoning that supports and correctly identifies the magnitude of the force that the student exerts on the scale when the student is at point P ?
FScale, because that is the magnitude of the force exerted by the scale on the student.
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? (hanging in a line all connected one to the next above)
FTension up (4 blocks), FTension down (2 blocks), Fgravity (2 blocks)
On the surface of Planet X, a 2 kg object is thrown upward with a speed of 20 ms. The object's vertical velocity as a function of time is shown in the graph. Which of the following free-body diagrams represents the gravitational force exerted on the object while it is in free fall?
Fgravity= 8N (Down 4 boxes)
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 θ0θ0 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.
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. 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 m/s by a total time of 5 s.
Three forces act on an object. If the object is in translational equilibrium, which of the following must be true? I. The vector sum of the three forces must equal zero II. The magnitudes of the three forces must be equal III. All three forces must be parallel.
I only
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.
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.
Distance (m)0.05 Speed (m/s)0.16 Force (N)0.050 A block of known mass M is on a disk that rotates about its center, as shown above. The block does not slip on the disk, and travels at a constant tangential speed v when at a distance R from the center with a centripetal force of magnitude F exerted on it. Which of the following statements about other quantities that might be determined is correct?
The centripetal acceleration of the block can be determined, since ac=v2r since the block's tangential speed is known and the radius is known. & The coefficient of friction between the block and the disk can be determined, since friction provides the centripetal force and the equation F=μmg can be applied.
A person is running on a track. Which of the following forces propels the runner forward?
The force of friction exerted by the ground on the person
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.
An object of unknown mass is swung in a vertical circle at the end of a light string, as seen in the figure above. A measurement is made of the object's tangential speed at the bottom circular path. A student must determine the tension in the string at the bottom of the circular path. Which of the following measurements, in conjunction with the object's tangential speed, are required to determine the tension in the string? Select two answers.
The object's mass & The diameter of the circular path
A student builds the apparatus shown above. A light string is attached to an object of unknown mass and passed through a tube such that the other end of the string is attached to a second object of mass M. By holding on to the tube, the student swings the object of unknown mass in a horizontal circle of radius r while the object of mass M hanging from the string remains at a constant height. In each trial, the radius r of the circular path is changed and the tangential speed ν of the object of unknown mass is calculated. How can the student determine the value of the unknown mass by using the radius of its circular path and its speed?
Use the slope of a graph of R as a function of ν^2.
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+1/2ayt^2 from the moment in time in which the ball was released to the moment in time in which the ball hits the ground.
A 5kg object is released from rest near the surface of a planet. The object's vertical position as a function of time is shown in the graph. Which of the following procedures can be used to determine the strength of the gravitational field on the planet?
Use y=y0+vy0t+1/2ayt^2. Use 10s for t, 0 ms for vy0, 400m for y0, and 0m for y. Solve for ay.
