projectiles, UCM, LUG exam - physics final
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.
-object's mass -diameter of the circular path
One end of a string is attached to the ceiling with the other end attached to a toy. The toy can be set into motion such that it travels in a horizontal circular path at a constant tangential speed, as shown above. Which of the following measuring tools, when used together, could be used to determine the time it takes for the toy to complete one revolution around the circle? Select two answers.
-protractor -meter stick
During an experiment, an object is placed on a disk that rotates about an axle through its center, as shown in Figure 1. The disk is a distance R =0.10 m from the center and rotates with a constant tangential speed of 0.60 ms. A free body diagram of the forces exerted on the block is shown in Figure 2 with an unknown force of friction. What is the force of friction exerted on the object?
0.72 N
A ball is attached to one end of a string such that the ball travels in a vertical circular path near Earth's surface. The force diagram of the ball at its lowest point in the circular path is shown above. What is the net centripetal force exerted on the ball?
15 N
A moon of mass 1×1020kg is in a circular orbit around a planet. The planet exerts a gravitational force of 2×1021N on the moon. The centripetal acceleration of the moon is most nearly
20 m/s^2
A 100 kg cart goes around the inside of a vertical loop of a roller coaster. The radius of the loop is 3 m and the cart moves at a speed of 6 m/s at the top. The force exerted by the track on the cart at the top of the loop is
200 N
A new planet is discovered that has twice the Earth's mass and twice the Earth's radius. On the surface of this new planet, a person who weighs 500 N on Earth would experience a gravitational force of
250 N
A child has a toy tied to the end of a string and whirls the toy at constant speed in a horizontal circular path of radius R. The toy completes each revolution of its motion in a time period T. What is the magnitude of the acceleration of the toy?
4π2R / T2
A satellite of mass 1000 kg is in a circular orbit around a planet. The centripetal acceleration of the satellite in its orbit is 5 ms2. What is the gravitational force exerted on the satellite by the planet?
5000 N
A car with speed v and an identical car with speed 2v both travel the same circular section of an unbanked road. If the frictional force required to keep the faster car on the road without skidding is F, then the frictional force required to keep the slower car on the road without skidding is
F/2
A planet of mass m orbits a star of mass M, where m<<M. The orbit is circular, its radius is r, and its period is T. True statements about the planet's orbit include which of the following? I. The orbital speed equals 2πr / T II. The gravitational force equals GMm / r2 III. If the orbital radius r were greater, T would also be greater.
I, II, and III
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 rock attached to a string swings in a vertical circle, as shown above, with negligible air resistance. Which of the following diagrams could correctly show all the forces on the rock when the string is in the position above?
arrow left and arrow down
One end of a string is attached to a vertical pole with the other end of the string attached to a ball that swings in a horizontal circular path, as shown. Which of the following free body diagrams represents the forces exerted on the ball?
arrow up and to the left, arrow down
A small block slides without friction along a track toward a circular loop. The block has more than enough speed to remain firmly in contact with the track as it goes around the loop. The magnitude of the block's acceleration at the top of the loop is
greater than zero but less than g
A rock of mass m is thrown horizontally off a building from a height h, as shown above. The speed of the rock as it leaves the thrower's hand at the edge of the building is vo How much time does it take the rock to travel from the edge of the building to the ground?
h/v0
A ball of mass m is attached to a vertical rod by two massless strings. The rod is rotated about its axis so that both strings are taut, with tensions T1 and T2, respectively. The strings and rod form the right triangle shown in the figure above. The ball rotates in a horizontal circle of radius r with speed v. What is the tension T1 in the upper string?
mg/(cosθ)
An object attached to one end of a string moves in a circle at constant speed. Which of the following is correct?
object is accelerating as it moves
A spacecraft is placed in a circular orbit around a planet with mass 6.4 x 1023 kg. The spacecraft orbits at a height of 4.5 x 107 m above the planet's surface. What additional information is needed to calculate the speed of the spacecraft in the orbit?
planet's radius only
