Phy 211 General Physics I Chapter 7 Worksheet KE and Work 1 1 A 50 kg box is pulled horizontally a distance of 5 m along a frictionless floor by a 300 N force a How much work is performed on the box b What is change in kinetic energy of the box c What is the horizontal velocity of the box at the end of the 5 m 2 A 50 kg box is pulled a distance of 5 m up a 30 o incline along a frictionless floor by a 300 N force a How much work is performed on the box b What is change in kinetic energy of the box c What is the velocity of the box at the end of the 5 m d If there is kinetic friction k 0 1 between the box and the incline how much work is performed on the box by the 300 N force e How much work is performed net on the box Is there a difference Why 3 According to the label a 2 oz Snickers candy bar contains 266 nutritional calories or kcal a How much energy in Joules is in one Snickers bar 1 kcal 1000 cal 4186 J b If an average person m 60 kg were eat a Snickers bar and use all of its energy for mechanical work how high could this person climb in elevation ignoring drag and friction c How fast could an average person accelerate to from rest using only the energy of this Snickers bar Apply the Work Energy Theorem to solve this problem d The average person expends approximately 1500 kcal per day just to maintain physiological function What is the power generated by an average person in Watts Phy 211 General Physics I Chapter 7 Worksheet KE and Work 2 4 Consider the 2 mass pulley system to the right where M1 10 kg and M2 20 kg Assume the pulley has no mass and there is no friction between i M 2 and the surface supporting it and ii the pulley itself M2 a If M1 drops a distance of 1 m how much work is performed on the block b How much work is performed on M 2 M1 c How much work is performed by the tension force on the 2 blocks d What is the kinetic energy of each block at the end of the drop e How fast are the two blocks moving at the end of the drop 5 An Amusement Park Ride Consider a dangling car attached to a massless rope as shown below The car rotates about the center at a speed of 30 m s rope and has a mass of 150 kg The radius of the circular path traveled by the car is 15 0 m a How much work is performed by the centripetal force on the car during one complete revolution v 30 m s b How much work is performed by the tension force in the rope on the car during one complete revolution car r 15 m 6 Joey 60 kg jumps out of a moving airplane and plummets to the ground During a particular phase of his descent vox 70 m s and voy 30 m s he travels downward 100 m against an average vertical air drag force of 310 N a What is the average net force exerted on Joey during this phase of descent b How much net work is performed on Joey Apply the Work Energy Theorem c How much work is performed by each force exerted on Joey d Express Joey s velocity vector at the end of this phase Phy 211 General Physics I Chapter 7 Worksheet KE and Work 3 7 A 2005 Corvette convertible coupe automobile was tested by Road Track magazine The following performance data were collected Tested Weight lb Mass kg mile time s Final speed mph Final speed m s 3275 1481 8 12 8 114 5 51 2 a What is the KE at the start of the trial v 0 mph b What is the KE at the end of the quarter mile c How much net work is performed on the Corvette during this trial d What is the average net power output in W or J s for the Corvette during this test e What is the average net power in horsepower hp Note 1 hp 745 7 W f What is the average speed in m s of the Corvette during this test g What is the average net force exerted on the Corvette during this trial h This Corvette has a top speed of 83 1 m s 186 mph What is the average force exerted by the Corvette when moving at top speed assuming it is operating at the power output determined in g What is the force of air drag against the Corvette i The engine in this Corvette model has rated maximum power output in hp of 400 hp Compare this rated value to the actual power output determined in part g by estimating the efficiency Phy 211 General Physics I Chapter 7 Worksheet KE and Work 4 Energy and Simple ideal Springs 8 A mass 0 5 kg is attached to a massless spring k 50 N m which is attached firmly to a wall at the other end The mass is initially pulled from position A to position B a displacement of 0 2 m then released Note there is no friction between the mass and the ground and the spring behaves as an ideal spring A k B m a What is the net force acting on the mass at position B just as it is released Apply Newton s 2nd Law b What is the force exerted by the spring on the mass at B c What is the force exerted by the spring on the mass at A d What is the average force applied to the mass as it moves from B to A e How much work does the spring perform to move the mass from B to A f What is the acceleration of the mass just as it is let go at B g When the mass returns to the initial rest position of the spring at A what is the acceleration of the mass h What is the velocity of the spring at position A i As the mass continues moving to the left how far does the mass overshoot from the rest position i e what is the displacement Why