MULUNGUSHI UNIVERSIT AULUNGUSHI UNIVERSITY CAMPUS LIBRARY ¢ OAN COLLECTION SCHOOL OF SCIENCE, ENGINEERING AND TECHNOLOGY DEPARTMENT OF MATHEMATICS AND SCIENCE PHY 101: INTRODUCTORY PHYSICS I 2020 SEMESTER 1 FINAL EXAM 23? DECEMBER, 2020 (14:00-17:00 HOURS) DURATION: 3 HOURS MARKS: 100 INSTRUCTIONS 1, This examination paper consists of two sections; Section A and Section B. Section A has 20 multiple choice questions, of which you must answer all. This section is compulsory. 2. Section B of this examination paper has four (4) questions, of which you are required to attempt any three (3). 3. All questions carry equal marks; the marks for each sub-question are indicated in square brackets. 4, Clearly indicate on the cover page of your answer booklet which questions you have ___ attempted. 5. Some equations and physical constants that you may find useful are given on the formula sheet provided. DO NOT TURN THIS PAGE UNTIL YOU ARE TOLD TO DO SO. Page 1 of 10Equations PHY 10] FORMULA SHEET - = tat GPE =mgh vi = vp + 2as T = sHsp t vot zat? T= nr ve sinO0) Feats 9 sin Fit = bp g F=ma W= Fs cosd T ee KE =5mv? ‘g = 9.80 m/s* Physical Constants and Other Useful Data M, = 598% 10°" kg [Re = 6.38 x 10° m | Moun = 1989 x 10°° kg L 6.67 x 10-7 N.m?/kg? © = 3.00 x 10° m/s Page 2 of 10SECTION A: ANSWER ALL QUESTIONS (40 MARKS) 1. There is no SI base unit for area because: ‘A. an area has no thickness; hence no physical standard can be built B. we live a three (not a two) dimensional world C.. it is impossible to express square feet in terms of meters D. area can be expressed in terms of square meters 2. Suppose A = BYC™, where A has dimensions L, B_ has _ dimensions Lz dimensions LT?. Then the exponents n and m have the values: A. 2/3; U3 B.2;3 C. 4/5; “1/5 D. 1/5; 3/5 3. Of the following situations, which one is IMPOSSIBLE? ‘A. A body having velocity east and acceleration east B. A body having constant velocity and variable acceleration C. A body having zero velocity and non-zero acceleration D. A body having constant acceleration and variable velocity 4, A ball is thrown straight upward with some initial speed. When it reaches the top of its flight (at a height h), a second ball is thrown straight upward with the same initial speed. Where will the balls cross paths? A. atheight h B. above height h/2 C. at height h’2 D. below height h/2 but above 0 5. You drop a rubber ball. Right after it leaves your hand and before it hits the floor, which of the plots below best represents the velocity versus time graph for this motion? (Assume your positive y-axis is pointing up.) Page 3 of 10Vt vi B yo TN NS MR SS 6. At the traffic lights, a truck traveling at 15 m/s passes a car as it starts from rest. The truck travels at constant velocity and the car accelerates at 3 m/s”. How much time does the car take to catch up with the truck? A. 5s B. 10s c. 15s D. 20s 7. A vector of magnitude 20 is added to a vector of magnitude 25. The magnitude of the sum might be: A. zero B. 3 c 12 D. 47 8, A small cart is rolling down an inclined track and accelerating. It fires a ball straight out of the cannon as it moves. After it is fired, what happens to the ball? A it depends upon how much the track is tilted B. it falls behind the cart C. it falls in front of the cart D it falls right back into the cart 9. Two bodies are falling with negligible air resistance, side by side, above a horizontal plane. If one of the bodies is given an additional horizontal acceleration during its descent, it A. strikes the plane at the same time as the other body strikes the plane earlier than the other body B, C. has the vertical component of its velocity altered D. has the vertical component o acceleration altered Page 4 of 1010, An object rests on a horizontal frictionless surface. A horizontal force of magnitude F is applied, This force produces an acceleration: A. only if F is larger than the weight of the object B, only while the object suddenly changes from rest to motion, C. always D. only if the inertia of the object decreases 11. A car moves horizontally with a constant acceleration of 3 m/s”. A ball is suspended by a string from the ceiling of the car. The ball does not swing, being at rest with respect to the car. What angle does the string make with the vertical? AT B. 35° C. 52° D. 73° 12. The “reaction” force does not cancel the “action” force because: ‘A. the action force is greater than the reaction force B. they are on different bodies . they are in the same direction D. the reaction force exists only after the action force is removed 13, A motor bike travels north at constant velocity. It goes over a piece of mud, which sticks to the tire. The initial acceleration of the mud, as it eaves the ground, is: A. vertically upward B. horizontally to the north C. horizontally to the south D. zero 14. A certain car, going with a speed of v1, rounds a level curve of radius R; in such a way that it is just on the verge of skidding. If the car’s speed is doubled, what is the tightest curve on the same road that it can round without skidding? A.2R, B. 4R, C.R/2 Page 5 of 10D. Ry/4 15, A rocket ship is coasting toward a planet. Its captain wishes to know the value of g at the surface of the planet. This may be inferred by: A. measuring the apparent weight of one of the crew B. observing the ship’s acceleration and correcting for the distance from the center of the planet. C. measuring the diameter of the planet D. measuring the density of the planet 16. The amount of work required to stop a moving object is equal to: A. the velocity of the object B. the kinetic energy of the object C. the m: of the object times its acceleration D. the mass of the object times its velocity 17. A person holds an 80-N weight 2m above the floor for 30 seconds. The power required to do this is: A.80W B. 40W c.20W D. none of these 18, A small car and a large truck collide head-on and stick together. Which one has the larger momentum change? A. The car B. The truck _ C. They both have the same momentum change D. Can’t tell without knowing the final velocities 19. Aman, with his arms at his sides, is spinning on a light frictionless tumtable, When he extends his arms: A. his angular velocity increases B. his angular momentum remains the same C. his rotational inertia decreases Page 6 of 10D. his rotational kinetic energy increases 20. A window washer attempts to lean a ladder against a frictionless wall. He finds that the ladder slips on the ground when it is placed at an angle of less than 75 to the ground but remains in place when the angle is greater than 75e. The coefficient of static friction between the ladder and the ground: A. is about 0.13 B. is about 0.27 C. is about 1.0 D. depends on the mass of the ladder Page 7 of 10SECTION B: ATTEMPT ANY THREE (3) QUESTIONS QUESTION ONE (1) (a) Describe an experiment you would perform to demonstrate that in the absence of air resistance, objects fall at the same rate regardless of their mass. (3) (b) A car and a truck are heading directly toward each other on a straight and narrow road, but they avoid a head-on collision by simultaneously applying their brakes at ¢ = 0. The resulting velocity-versus-time graphs are shown in the figure below womys) 15 0 5 o 16) s -10 15 (i) From the graph, identify the lines representing the motion of the truck and that of the car. Explain your response. (2) i) What is the separation between the car and the truck when they have come to rest, given that at ¢= 0 the car is at x= 15 m and the truck is at x = -35 m? 6] (c) Define the term ‘free fall” as understood in the physics context. 2) (d) A football is kicked at an angle of 37.0° with a velocity of 20 m/s. Calculate (i) The time taken for the ball to reach the maximum height, [4] (ii) The ball’s velocity (magnitude and direction) at the moment when it is just about to hit the ground. Bl QUESTION TWO (2) (a) What is meant by an ‘inertial’ frame of reference? 2] (b) As two boats approach the marina, the velocity of boat I relative to boat 2 is 2.15 m/s in a direction 47.0° east of north. If boat 1 has a velocity that is 0.775 m/s due north, what is the velocity (magnitude and direction) of boat 2? (8) (©) Why is it easier for a truck to get stuck on a muddy road when it is empty than when it is loaded 2 Page 8 of 10(d) 2 boxes are connected by a cord running over a pulley as shown in the figure below. The coefficient of kinetic friction between box A and the table is 0.2. Ignore mass of cord and pulley and friction in the pulley, Soke Find (i) The acceleration of the system, (6) ii) Tension in the cord. (2) QUESTION THREE (3) (a) A woman places her briefcase on the backseat of her car. As she drives to work, the car negotiates an unbanked curve in the road that can be regarded as an are of a circle of radius 62.0 m, While on the curve, the speed of the car is 15.0. m/s at the instance the briefcase starts to slide across the backseat toward the side of the car. (i) What force causes the centripetal acceleration of the briefcase when it is stationary relative to the car? 2) (ii) Under what condition does the briefcase begin to move relative to the car? 2 (iii) Calculate is the coefficient of static friction between the briefcase and seat surface? 7] (b) A 1 kg block situated on a rough incline is connected to a spring of spring constant 100 N m! as shown below. The block is released from rest with the spring in the unstretched position. The block moves 10 em down the incline before coming to rest. Find the coefficient of friction between the block and the incline. Assume that the spring has a negligible mass and the pulley “is frictionless. 9] k= 100m Page 9 of 10QUESTION FO! (4) (@) A circular curve of radius R in a new highway is designed so that a car travelling at a speed v0 can negotiate the turn safely on glare ice (zero friction). If a car travels too slow, then it will slip towards the center of the circle. Ifit travels too fast, then it will slip away from the center of the circle. If the coefficient of static friction increases, a car can stay on the road while travelling at any speed within the range vmin to mex. Show that vmin and vmax can, respectively, be given by the equations vay, [EE MeRa/ 0B) —_— imax = V0 VG pave /R) a i () A bicycle wheel is mounted so that it can rotate horizontally as shown. ‘The wheel has a mass of 0.79 kg and radius of 0.45 m, and the masses of the spokes and axle are negligible. (i) Show that the moment of inertia of the wheel is 0.16 kg m?, ol (ii) A constant driving force of 20 N is applied tangentially to the rim of the wheel. Calculate the magnitude of the driving torque on the wheel. fal Giii)A constant frictional torque of 1.5 N m acts on the wheel. Calculate the angular acceleration of the wheel. ii) (iv) After a period of 4s, and assuming the wheel starts from rest, calculate: (A) the total angular displacement of the wheel, ri (B) the angular velocity of the wheel, 1 (C) the kinetic energy of the wheel 0 (v) The driving force is removed after 4s. Calculate the time taken for the wheel to come to rest. 12] (c)-A satellite orbits the Earth with a period of 95 min. Calculate the height of the satellite above the Earth’s surface. (2) END OF EXAM Page 10 of 10