6-3 Kinetic Energy; Work-Energy Principle IS 16. i I8. 19, 20). (I) At room temperature. an oxygen molecule. with mass of 5.31 X 107*kg, typically has a KE of about 6.21 % 1072' J. How fast is the molecule moving? (I) (a) If the KE of an arrow is doubled. by what factor has its speed increased? (b) If its speed is doubled. by what factor does its KE increase\"? (I) How much work is required to stop an electron (m=911x10 3'kg) which is moving with a speed of 1.90 % 10m/s? (I) How much work must be done to stop a 1250-kg car traveling at 105 km/h? (IT) An 88-g arrow is fired from a bow whose string exerts an average force of 110N on the arrow over a distance of 78 cm. What is the speed of the arrow as it leaves the bow? (IT) A baseball (m = 140g) traveling 32m/s moves a fielder's glove backward 25 cm when the ball is caught. What was the average force exerted by the ball on the glove? . (IT) If the speed of a car is increased by 50%, by what factor will its minimum braking distance be increased, assuming all else is the same? Ignore the driver's reaction time. 6-4 and 6-5 Potential Energy 26. 27. 29. (I) A spring has a spring stiffness constant. k. of 440 N/m. How much must this spring be stretched to store 2517 of potential energy? (I) A 7.0-kg monkey swings from one branch to another 1.2m higher. What is the change in potential energy? . (I) By how much does the gravitational potential energy of a 64-kg pole vaulter change if his center of mass rises about 4.0 m during the jump? (IT) A 1200-kg car rolling on a horizontal surface has speed = 65km/h when it strikes a horizontal coiled spring and is brought to rest in a distance of 2.2 m. What is the spring stiffness constant of the spring