College Physics I 1401 Spring Final 120 Minutes 200 Points Instructor Dr Ping Lu Student Name Grade Notes Please give me your all working on each question For instance 15 points A grocery bagger pushes a 2 00 kg bag of potatoes in such a way that the net external force on it is 65 0 N Calculate its acceleration Given m 2 00 kg F 65 0 N Find a Solve From the second law F ma so we have a F m 65 0 2 00 32 5 m s 2 Answer Its acceleration is 32 5 m s 2 All working on each question you should have four steps given find solve and answer 1 Multiple Choice total 80 points 1 State how many significant figures are proper in the results of the following calculation 106 7 90 46 210 1 01 a 1 b 2 c 3 d 4 2 State how many significant figures are proper in the results of the following calculation 5 9 2 a 1 b 2 c 3 d 4 3 What is the magnitude of the momentum of a 7000 kg truck whose speed is 20 m s Answer 4 How much work does a supermarket checkout attendant do on a can of soup he pushes 0 310 m horizontally with a force of 5 20 N Express your answer in joules and kilocalories Answer 5 The density of brass is 8 6 g cm3 What is this value in kilograms per cubic meter kg m 6 Assume that an MX missile goes from rest to a suborbital velocity of 6 0 km s in 40 0 s What is its average acceleration in m s 2 What is its average acceleration in multiples of g 7 A stone is thrown horizontally from the top of a cliff One second after it has left you hand its vertical distance below the cliff is 8 Compared to the mass of a certain object on earth the mass of the same object on the moon is a more b less c the same 9 When the net force that acts on a hockey puck is 12 N the puck accelerates at a rate of 48 m s s Determine the mass of the puck 10 Calculate the linear acceleration of a car the 0 30 m radius tires of which have an angular acceleration of 12 0 rad s2 Assume no slippage Answer 2 Questions total 120 points 1 10 points A grocery bagger pushes a 1 00 kg bag of potatoes in such a way that the net external force on it is 20 0 N Calculate its acceleration 2 15 points An ordinary workshop grindstone has a radius of 9 50 cm and rotates at 7000 0 rpm Calculate the centripetal acceleration at its edge in m s s and convert it to multiples of g 3 Suppose a yo yo has a center shaft 0 300 cm in radius and that string is being pulled from it 10 points a If the string is stationary and the yo yo accelerates away from it at a rate of 1 70 m s2 what is its angular acceleration 5 points b What is the angular velocity after 0 750 s if it starts from rest 5 The outside radius of the yo yo is 3 50 cm In the reference fram of the yo yo s mass center what is the tangential acceleration of a point on its edge 4 Suppose a 57 0 kg gymnast climbs a rope a 8 points What is the tension in the rope if he climbs at a constant speed b 7 points What is the tension in the rope if he accelerates upward at a rate of 1 80 m s2 5 15 points The triceps muscle in the back of the upper arm extends the forearm This muscle in a professional boxer exerts a force of 2 00 103 N with an effective perpendicular lever arm of 4 00 cm producing an angular acceleration of the forearm of 130 rad s2 What is the moment of inertia of the boxer s forearm 6 8 points a How much gravitational potential energy relative to the ground on which it is built is stored in an Egyptian pyramid given its mass is about 6 109 kg and its center of mass is 28 0 m above the surrounding ground 7 points b What is the ratio of this energy to the daily food intake of a person 1 2 107 J 7 15 points A 5 50 105 kg subway train is brought to a stop from a speed of 0 600 m s in 0 900 m by a large spring bumper at the end of its track What is the force constant k of the spring 8 8 points a Calculate the force needed to bring a 1000 kg car to rest from a speed of 90 0 km h in a distance of 116 m a fairly typical distance for a nonpanic stop 7 points b Suppose instead the car hits a concrete abutment at full speed and is brought to a stop in 2 00 m Calculate the force exerted on the car and compare it with the force found in part a i e find the ratio of the force in part b to the force in part a