Two cars are moving. The first car has thrice the mass of the second car but only 1/3 as the kinetic energy. When both cars increase their speed by 9 m/s, they then have the same kinetic energy. Calculate the original speeds of the first car. a. 15.59 m/s2 c. 2.35 m/s2 b. 5.20 m/s2 d. 5.30 m/s2

6. Two blocks are connected by a very light string passing over a massless, frictionless pulley (see figure). Traveling at a constant speed, the 20.0-N block moves 65.0 cm to the right and the 12.0-N block moves 65.0 cm down. How much work is done a. on the 12.0-N block by gravity? b. on the 12.0-N block by the tension in the string? in total on the 12.0-N block? C. d. on the 20.0-N block by gravity? on the 20.0-N block by the tension in the string? on the 20.0-N block by the normal force? on the 20.0-N block by friction? in total on the 20.0-N block? e. f. g. h. 20.0 N 12.0 N

choose the letter of the correct answer only! Find the kinetic energy of a car with mass 1000kg moving at speed of 30 m/s. *   A. 15 000 J B. 900 000 J C. 500 000 J D. 350 000 J E. 450 000 J

A. Ignoring air drag, what is the takeoff speed of such a flea? (in m/s) B. Calculate the kinetic energy of this flea at takeoff (in J) C. Calculate the kinetic energy per kilogram of mass (in J/kg) D. If a 73.0 kg, 1.80 m tall human could jump to the same height compared with his length as the flea jumps compared with its length, how high could the human jump? (in m) E. If a 73.0 kg, 1.80 m tall human could jump to the same height compared with his length as the flea jumps compared with its length, what takeoff speed would the man need? (in m/s) F. Most humans can jump no more than 60.0 cm from a crouched start. What is the kinetic energy per kilogram of mass at takeoff for such a 73.0 kg person? (in J/kg)

1. a brick with mass 30 kg rests a top a 12 m tall wall. What is the brick's gravitational potential energy relative to the ground? a. 2400 J b. 360 J c. 240 J d. 3600 J 2. A brick with mass 20 kg rests atop a 12 m tall wall. The brick is nudged off the wall, and falls to the ground. How fast will the brick be going as it hits the ground? Neglect air resistance. a. 12 m/s b. 120 m/s c. 0 m/s d. 15.5 m/s

19. Using a rope, you pull a large 150 kg sled while accelerating at 0.2 m/s² across a horizontal (level) but icy surface. For a coefficient of kinetic friction between the sled an ice is 0.1. Calculate the total work when pulling the sled, a distance of 10 m. a. b. 30 Joules 300 Joules C. 1500 Joules d. 1800 Joules e. None of these are correct

A 10 kg car starts from the rest and goes 5m/s. How much work is done by the car? (Hint :use work energy theorem to calculate work)   A. 25 J   B. 250 J   C. 50 J   D. 125 J

150 kg object is at a height of 12 m. A.) How many joules of kinetic energy does it gain when it falls to the ground?  B.) Using concepts of energy, find the speed of the object in meters per second just before it hits the ground.