Unit 3

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 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 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

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

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

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

Determine the slope of the best fit line and set it equal to μSg.

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 r

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.

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 th

FScale, because that is the magnitude of the force exerted by the scale on the student.

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 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 de

Mass balance, meterstick, and timer

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.

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 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.

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.

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

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 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

Use the slope of a graph of R as a function of ν^2.

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.

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 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 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.