Physics 115 Mock Midterm Sunday, October 18, 6pm

Transcription

1 Physics 115 Mock Midterm Sunday, October 18, 6pm Note: This mock test consists of questions covered in Physics 115. This test is not comprehensive. The problems on this test were created by your SSS peer mentors, and not your professors, and are based on textbook problems, problems from old exams, etc. **This mock test should not be viewed as a preview of the actual test, and you should not rely solely on it for your test preparation.** 1. The diameter of the Milky Way is approximately 1.2 x 10 5 light years. Estimate this distance in meters. a) m b) m c) m d) m 2. Convert 3.6 gallons to ml given the following conversion factors. 1 gallon = 4 quarts, 1 quart = 4 cups, 1 cup = 8 ounces, 1 ounce = ml. a) ml b) ml c) ml d) ml Questions 3-5 refer to the following: A cannon fires two identical cannonballs with the same kinetic energy. The first cannonball is fired 30 above the horizontal, with total travel time T 1 and reaching a maximum height H 1. The second cannonball is fired at 45 above the horizontal, with total travel time T 2 and reaching a maximum height of H 2. Neglect air resistance. 3. What is the ratio of their travel times, T 1:T 2? a) 1 : b) 2 : c) : 2 d) : 1 4. What is the ratio of their maximum heights, H 1:H 2? a) H 1:H 2 = 1 : 2 b) H 1:H 2 = 2: 1 c) H 1:H 2 = 1: 3 d) H 1:H 2 = 3 : 1

2 5. If one were to try to catch a cannonball in mid-air while at maximum height, which cannonball would be LEAST damaging? a) They would be EQUALLY damaging, as they start off with identical kinetic energy b) Cannonball 1 would be less damaging, as has lesser kinetic energy at max height c) Cannonball 2 would be less damaging, as it has lesser potential energy at max height d) Cannonball 2 would be less damaging, as it has lesser kinetic energy at max height 6. A car moving at 20m/s slams on its brakes and comes to a stop after 40m. Find the coefficient of friction between the car tires and the road. a) 0.5m b) 0.25 c) 0.51 d) A driver approaches a train crossing and slams on the brakes of his 6000kg truck. His initial speed is 50km/h and he has 20m to stop before hitting the train. If the maximum force his brakes can take before breaking is 40000N, will the truck collide with the train? a) Yes b) No 8. A crate remains stationary after it has been placed on a ramp inclined at an angle with the horizontal. Which of the following is true of the frictional force on the crate? a) It is larger than the weight of the crate b) It is at least equal to the weight of the crate c) It is equal to µsn d) It is equal to the component of the gravitational force acting down the ramp 9. A woman is on an elevator moving up with an acceleration of 0.2g. What is the force exerted on her by the floor? a) m(0.8g) b) m(1.0g) c) m(1.2g) d) m(0.2g) 10. A box of mass 100 kg is being pulled with a force of 500 N at an angle 30 o. What is the normal force exerted by the ground on the box? a) 1230 b) 730 c) 1413 d) 547

3 11. If a book (book1) is placed on a rough table and pushed from point A to D, and another book (book2) of the same mass is pushed from point A to B to C to D (see diagram). Which of the following statements is true? a) The work done to each book is the same b) The work done to book1 > book2 c) The work done to book2 > book1 12. Suppose a 60kg person decides to slide down a 21.9m waterslide in a water park. If the person is clocked at 18.0 m/s at the bottom of the slide, find the work done on the person by friction. a) 3160 J b) J c) 1580 J d) J 13. A spring with spring constant k is compressed a distance d from its equilibrium position. When the spring is released, it pushes a mass m up a frictionless ramp that is at an angle α to the horizontal. Find an expression for the maximum distance, Y, that the mass travels up the ramp. a) Y = b) Y = kd2 2mg c) Y = kd2 2m d) Y = kd 2 2mg(sin(α)) kd 2 2m(sin(α)) 14. Two engines are used to lift bricks to the top of a building under construction. Engine 1 lifts the bricks straight up to the building top. Engine 2 lifts the bricks across a frictionless ramp that goes all the way up to the top of the building. If both engines were designed to supply the exact same amount of power to lift the same amount of bricks, which of the following statements is true? a) The force applied by engine 1 equals the force applied by engine 2 b) The speed of bricks lifted by engine 1 equals the speed of bricks lifted by engine 2 c) The force applied by engine 1 is less than the force applied by engine 2 d) The time it takes engine 1 to accomplish the task is equal to the time required by engine 2

4 15. A 3000 kg car is starting from rest, accelerates for 5.00s. The magnitude of the acceleration is a = 5 m/s 2. Determine the average power generated by the engine that is accelerating the car. a) W b) W c) W d) W 16. A 4.00 kg ball is traveling at 5.00 m/s and strikes a wall. The 4.00 kg ball bounces off the wall with a velocity of 4.0 m/s. The change in momentum of the ball is a) kg m/s b) kg m/s c) 30 kg m/s d) -36 kg m/s 17. An object of mass m is dropped from height h on a board that is attached to a spring with spring constant k causing it to compress by length d (see figure below). What equation (in terms of k, d, m, and g) represents the height h from which the block was dropped? a) h = kd2 mgd b) h = kd2 2mgd c) h = kd2 2mg + d d) h = kd2 2mg d e) h = 2mgd kd A ball collides with a second ball at rest. After the collision, the first ball comes to rest and the second ball moves off at the speed of the first ball. In this collision: a) total momentum is not conserved b) total kinetic energy is not conserved c) total momentum is conserved but total kinetic energy is not conserved d) total momentum is not conserved but total kinetic energy is conserved e) total momentum and total kinetic energy are conserved and the masses are equal

5 19. Two satellites are in orbit about the Earth with the same orbital radius. Satellite B has twice the mass of satellite A. The radial acceleration of satellite B has a magnitude that is a) The same as the magnitude of the radial acceleration of satellite A b) One half the magnitude of the radial acceleration of satellite A c) Two times the magnitude of the radial acceleration of satellite A 20. A rifle fires a bullet. Immediately after the bullet is fired, which of the following is NOT true? a) the rifle and the bullet have the same magnitude of momentum b) the force on the rifle due to the bullet and the force on the bullet due to the rifle have the same magnitude c) the impulse on the rifle due to the bullet and the impulse on the bullet due to the rifle have the same magnitude d) the rifle and the bullet do not have the same kinetic energy e) the rifle and the bullet have the same kinetic energy Long Answer 1. An engineering student replaced the speedometer on the Agro s Ag Bag Drag car to read the speed in m/s as opposed to km/h. Unknowingly the poor agriculture student drives the car at a speed reading 50 on the speedometer. A cop nearby sees the agriculture student and begins chasing him as soon as the Ag Bag Drag car passes the officers vehicle. The cop car accelerates at a rate of 10m/s 2. How far will the cop car have to travel in order to catch up and end up beside the Ag Bag Drag car if the student continues to travel at a reading of 50 on the speedometer? How fast is the cop car going when this happens? 2. A rescue helicopter is trying to save a group of sailors stranded on a life raft. However, a storm is underway, and the wind pushes the helicopter eastward with a force of 1680 N, and the life raft eastward with 320 N force. The mass of the helicopter is 1350 kg including crew. The life raft has mass of 100 kg, with 4 sailors weighing 700 N each. If the helicopter s rotor blades provide a maximum lifting force of N. a) Find the acceleration of the life raft eastward. b) The helicopter is directly above the life raft and drops a rope. Find the lift force and angle made with the vertical, in order to hover steadily along with the life raft as it drifts. Refer to the diagram.

6 3. In the deep jungle, our hero Tarzan has a dangerous feat ahead of him. He must save his love Jane Porter who is stuck on a cliff-side ledge. Tarzan, who is on the other side of the cliff (15.6m away) and is 20m up, finds a 10m long rope and attaches it to a branch between the cliffs. To reach his beloved Jane, Tarzan swings down the rope so that it is taut throughout the entire flight and lets go of the rope when it is perfectly vertical, which occurs when he is 2m above Jane. Will Tarzan reach the other side without defying the laws of physics? Picture is not to scale. 4. The shuffleboard disks of equal mass, one orange, and the other green, are involved in a perfectly elastic glancing collision. The green disk is initially at rest and is struck by the orange disk moving initially to the right at 5.00 m/s. After the collision, the orange disk moves in a direction an angle of 37.0 with the horizontal axis while the green disk make an angle of 53.0 with this axis. Determine the speed of each disk after the collision. End of mock midterm Questions on this test have been created by peer mentors, or adapted from textbook exercises or old exam questions. Answers will be available at the Structured Study Session website.