Final MC questions for practice

Transcription

1 Final MC questions for practice 1) Whirl a rock at the end of a string and it follows a circular path. If the string breaks, the tendency of the rock is to A) continue to follow a circular path. B) follow a straight-line path. C) increase its speed. D) revolve in a smaller circle. 2) A 300-kg bear grasping a vertical tree slides down at constant velocity. The friction force between the tree and the bear is A) 30 N. B) 300 N. C) 3000 N. D) more than 3000 N. 3) An object at rest near the surface of a distant planet starts to fall freely. If the acceleration there is twice that of the Earth, its speed one second later would be A) 10 m/s. B) 20 m/s. C) 30 m/s. D) 40 m/s. 4) In each second of fall, the distance a freely falling object will fall is A) about 5 m. B) about 10 m. C) the same, but not 5 m or 10 m. D) increasing. 5) One half second after starting from rest, a freely falling object will have a speed of about A) 20 m/s. B) 10 m/s. C) 5 m/s. D) 2.5 m/s. 6) A rock is thrown vertically into the air. At the very top of its trajectory the net force on it is A) less than its weight. B) more than its weight. C) equal to its weight. 7) A 1-kg ball is thrown at 10 m/s straight upward. Neglecting air resistance, the net force that acts on the stone when it is halfway to the top of its path is about A) 1/2 N. B) 1 N.

2 C) 5 N. D) 7.5 N. E) 10 N. Answer: E 8) Two objects of the same size, but unequal weights are dropped from a tall tower. Taking air resistance into consideration, the object to hit the ground first will be the A) lighter object. B) heavier object. C) Both hit at the same time. D) not enough information 9) Earth pulls on the moon. Similarly the moon pulls on Earth, evidence that A) these two pulls comprise an action-reaction pair. B) Earth is larger so its pull is larger. C) the moon is smaller so its pull is smaller. D) larger objects pull harder. 10) A piece of rope is pulled by two people in a tug-of-war. Each pulls with 400 N of force. What is the tension in the rope? A) zero B) 400 N C) 600 N D) 800 N 11) A automobile and a baby carriage traveling at the same speed collide head-on. The impact force is A) greater on the automobile. B) greater on the baby carriage. C) the same for both. 12) The force on an apple hitting the ground depends upon A) the speed of the apple just before it hits. B) the time of impact with the ground. C) whether or not the apple bounces. D) all of these 13) You're driving down the highway and a bug spatters into your windshield. Which undergoes the greater change in momentum during the time of contact? A) the bug B) your car C) both the same 14) A 1000-kg car and a 2000-kg car are hoisted the same distance. Raising the more massive car requires A) less work.

3 B) as much work. C) twice as much work. D) four times as much work. E) more than four times as much work. 15) An object at rest may also have A) speed. B) velocity. C) momentum. D) kinetic energy. E) potential energy. Answer: E 16) Two 5000-kg passenger cars roll without friction (one at 1 m/s, the other at 2 m/s) toward each other on a level track. They collide, couple, and roll away together with a combined momentum of A) zero. B) 5000 kg m/s. C) 10,000 kg m/s. D) 15,000 kg m/s. 17) When a twirling ice skater brings her arms inward, her rotational speed A) increases. B) decreases. C) remains the same. 18) If the Earth rotated more slowly about its axis, your apparent weight would A) increase. B) decrease. C) stay the same. D) be zero. 19) A ring and a disk, initially at rest, roll down a hill together. The one to reach the bottom first A) is the ring. B) is the disk. C) depends on the masses. D) depends on the relative rotational inertias. E) Both reach the bottom at the same time. 20) If the Earth's mass decreased to one-half its original mass with no change in radius, then your weight would A) decrease to one quarter your original weight. B) decrease to one half your original weight. C) stay the same. D) none of these 21) The fastest moving planet in a solar system is

4 A) the smallest planet. B) the most massive planet. C) the planet nearest the sun. D) the planet farthest from the sun. E) any planet, for they all move at the same speed. 22) Which of the following is not a compound? A) air B) ammonia C) water D) salt E) All are compounds. 23) A force that determines the chemical properties of an atom is a(n) A) friction force. B) nuclear force. C) gravitational force. D) electrical force. 24) The reason a granite block is mostly empty space is that the atoms in the granite are A) in perpetual motion. B) mostly empty space themselves. C) held together by electrical forces. D) not as close together as they could be. E) invisible. 25) What is the molecular mass of a water molecule? A) 10 amu B) 12 amu C) 15 amu D) 18 amu E) None of these. It depends on the temperature. 26) What is the buoyant force acting on a 10-ton ship floating in the ocean? A) less than 10 tons B) 10 tons C) more than 10 tons D) depends on density of sea water 27) Airplane flight best illustrates A) Archimedes' principle. B) Pascal's principle. C) Bernoulli's principle. D) Boyle's law.

5 28) The air in this room has A) mass. B) weight. C) energy. D) all of these 29) Before ice can form on a lake, all the water in the lake must be cooled to A) zero degrees C. B) 4 degrees C. C) minus 32 degrees C. D) None of the above. Ice can form at the surface regardless of the water temperature below. 30) When an iron ring is heated, the hole becomes A) smaller. B) larger. C) neither smaller nor larger. D) either smaller or larger, depending on the ring thickness. 31) As a piece of metal with a hole in it cools, the diameter of the hole A) increases. B) decreases. C) remains the same. 32) Consider a sample of ice at 0 degrees C. If the temperature is decreased, the volume of the ice A) increases. B) decreases. C) stays the same. 33) Your feet feel warmer on a rug than on a tile floor because a rug A) is usually warmer than tile. B) is a better insulator than tile. C) for the same mass has more internal energy than tile. D) all of these 34) Cold water will warm to room temperature faster in a A) black pot. B) silver pot. C) depends more on the size of the pots than their color 35) An object will normally be a net radiator of energy when its temperature is A) higher than its surroundings. B) lower than its surroundings. C) neither of these

6 36) When a gas is changed to a liquid state, the gas A) releases energy. B) absorbs energy. C) neither releases nor absorbs energy. D) both releases and absorbs energy. 37) We are warmed by condensation because water molecules in the air that strike our bodies A) transfer some of their kinetic energy to us. B) gain kinetic energy as they change state. C) form an insulating layer on our bodies. 38) The voltage across the input terminals of a transformer is 110 V. The primary has 50 loops and the secondary has 25 loops. The voltage the transformer puts out is A) 25 V. B) 55 V. C) 110 V. D) 220 V. 39) A step-up transformer has a ratio of one to ten. Neglecting slight losses, if 100 W of power go into the primary coil, the power coming from the secondary coil is A) 1 W. B) 10 W. C) 100 W. D) 1000 W. 40) A device that transforms mechanical energy into electrical energy is a A) generator. B) motor. C) transformer. D) magnet. 41) Two charges separated by one meter exert 1-N forces on each other. If the charges are pulled to 3-m separation distance, the force on each charge will be A) 0.33 N. B) 0.11 N. C) 0 N. D) 3 N. E) 9 N. 42) Compared to the resistance of two resistors connected in series, the same two resistors connected in parallel have A) more resistance. B) less resistance. C) the same resistance.

7 43) The force on an electron moving in a magnetic field will be the largest when its direction is A) the same as the magnetic field direction. B) exactly opposite to the magnetic field direction. C) perpendicular to the magnetic field direction. D) at an angle other than 90 degrees to the magnetic field direction. 44) John's face is 20 cm in front of a concave shaving mirror. If he observes his image to be twice as big and erect, what is the focal length of the mirror? A) 10 cm B) 20 cm C) 30 cm D) 40 cm 45) An object is placed at a distance of 30 cm from a thin convex lens along its axis. The lens has a focal length of 10 cm. What are the values, respectively, of the image distance and magnification? A) 60 cm and 2.0 B) 15 cm and 2.0 C) 60 cm and 0.50 D) 15 cm and ) John's face is 20 cm in front of a concave shaving mirror. If he observes his image to be twice as big and erect, what is the focal length of the mirror? A) 10 cm B) 20 cm C) 30 cm D) 40 cm 47) Two point charges of magnitude µc and µc are placed along the x-axis at x = 0 cm and x = 40.0 cm, respectively. Where must a third charge, q, be placed along the x-axis so that it does not experience any net force because of the other two charges? A) 1.38 m B) m C) m D) m 48) A rectangular coil lies flat on a horizontal surface. A bar magnet is held above the center of the coil with its north pole pointing down. If the magnet is dropped from this position what is the direction of the induced current in the coil? A) There is no current in the coil. B) counterclockwise C) clockwise D) Not enough information is provided. 49) The primary coil of a transformer has 100 turns and its secondary coil has 400 turns, if the ac voltage applied to the primary coil is 120 V, what voltage is present in its secondary coil? A) 100 V B) 30 V

8 C) 480 V D) 400 V 50) The primary coil of a transformer has 600 turns and its secondary coil has 150 turns. If the ac current in the primary coil is 2 A, what is the current in its secondary coil? A) 8 A B) 1/2 A C) 2 A D) 4 A