1 Final exam 8 conceptual questions and 8 problems for 3 hours on Monday May 5 2014 Course PHYS1111 Instructor Tho Nguyen First and last name Student ID 1 A baseball is thrown vertically upwards into the air neglect air resistance and returns to where it started Based on the definition of speed and velocity justify each of these statements by stating whether they are true T or fall F Put the answer in front of each statement The average speed is not zero The total displacement is not zero The initial velocity and final velocity are equal The average velocity is zero The initial speed and final speed are equal The average acceleration is zero 2 You are driving your car mass m over a circular shaped bump in the road that has a radius r The normal force apparent weight of your car when it passes the bump is a larger than the m g b equal to m g c smaller than m g d not be able to determine The weight is m g 3 The metal head of a hammer with a wood handle is loose To tighten it you drop the hammer down onto a table Circle the correct answer i Should you a drop the hammer with the handle end down b drop hammer with the head end down or c do you get the same result either way ii What law did you use for your decision in i a Newton s first law b Newton s second law c Newton s third law 4 A barrel mass mLoad is attached to a massless rope which is attached to a hook mass mHook which is attached to the massless cable of a crane see the figure The cable is accelerating up with an acceleration Circle the correct answer i What is the tension of the rope a mLoad g b mLoad a c mHook mLoad d mHook mLoad g a e mLoad g a g a ii What is the tension of the cable a mHook a b mHook mLoad g a c mHook g a d mHook mLoad g a e mLoad g mHook a 2 5 A car accelerates from rest to a certain velocity in a certain time Assume that there is no friction and that the engine power is constant Consider the following scenarios independently using either P W t and work energy theorem or P F v i How long would it take to reach half the velocity also from rest a Half the time b One fourth the time c Double the time d Four times the time ii How long would it take to reach the same velocity if the engine had twice the power a Half the time b Same time c Double the time d Four times the time iii If you decrease the velocity two times the force that the engine exerts to run the car would a Increase two times b Decrease two times c Remain the same 6 Choose whether each of the following statements is true T or false F A system of particles with zero kinetic energy must also have zero momentum An object at rest on a frictionless surface is struck by a second object After the collision both objects must be moving A system of particles with zero momentum must also have zero kinetic energy It is possible for two isolated objects to collide so that all the initial kinetic energy of the system is lost Two cars collide at an intersection but do not stick together after the collision Therefore the collision was elastic 7 The rotating systems shown below differ only in that the two spherical movable masses are positioned either far from the axis of rotation left or near the axis of rotation right i Which statement is correct a Moment of inertia of the left system is smaller b Moment of inertia of the right system is smaller c Moments of inertia of them are the same ii If the hanging blocks are released simultaneously from rest which statement is correct a The block at left lands first b The block at right lands first c Both block land at the same time 8 A playground merry go round spins about its axis with negligible friction A child moves from the center of the merry go round to the rim For this system indicate which of the following quantities changes C and unchanges U Mass Moment of inertia Angular speed Rotational kinetic energy Potential energy Angular momentum 3 9 gravity From the Newton s law of universal gravitation one can get the free fall acceleration closed to the surface of the planet where G 6 67x10 11 N m2 kg2 M and R is the mass and radius of the planet a What is the free fall acceleration at the surface of the Mars Given mass of the Mars M 6 42x1023Kg and its radius R 3 39x106 m b Compare the weight of a man with mass m 100kg when he is on the surface of the Mars PM and the Earth PE Given the free fall acceleration of the Earth g 9 81m s2 c Suppose two apples are dropped at the same height a few meters from the surface of the Mars and Earth In what case does the apple reach the surface first Explain qualitatively your decision 4 10 relative motion You are riding a boat whose speed relative to the water 6 1m s The boat points at an angle of 25o upstream on a river flowing at 1 4m s a What is your velocity relative to the ground magnitude and angle b If the river is 300 m wide how far downstream has the boat moved by the time it reaches the north shore Hint addition of two vectors v13 x v12 x v23 x v13 y v12 y v23 y You need to know x and y components of vector v12 and v23 in order to calculate the components of vector v13 From here you are able to calculate the magnitude and the angle v13 5 11 projectile motion A projectile is launched from ground level at 33 0 m s at an angle of 30 0 above horizontal Use the launch point as the origin of your coordinate system a Calculate the initial velocity in x and y direction b How far downrange the horizontal distance from the origin was the projectile when it reached the highest point in its flight 6 12 Newton s law A 4 00kg sled is pulled across a surface without friction The force acting on the sled is of magnitude 6 0N and points in the direction 300 above the horizontal The sled starts at rest Given g 9 81m s2 a b c d e f Find the x and y components of vector F Find the normal force acting on the sled Find the acceleration of the sled How fast is it going after being pulled for 2s Find the work done by F after being pulled for 2s Find the power of F 7 …
View Full Document
Unlocking...