Please help just need answers to see if I got them right.

1. At room temperature, an oxygen molecule, with a mass of 5. 13x10-26 kg, typically has a kinetic energy of about 6.21x10-21 3. How fast is the molecule moving? 2.What is the efficiency of a machine in which 5700 ] is required to raise a 1250 N object 1. 25 m? Record your answer as a percentage and round to the nearest whole number. 3. When is efficiency of a process less than 100%? a. If work is done against gravity b. Always c. When you get more work out than you put in d. Only when humans are involved 4.A boy pulls a boat a distance of 50.0 m along a dock using a rope that makes a 25.0 angle with the horizontal. How much work is done on the boat by the boy if he pulls with a force of 680 N on the rope? Round your answer to the nearest whole number and include units. 5. How much work did the movers do (horizontally ) pushing a 160 kg crate 10.3 m across a rough floor, at a constant velocity, where the coefficient of friction between the box and the floor is 0.50? Round your answer to the nearest whole number and include units. 6. A roller coaster car starts out at rest at the top of the first hill and reaches a speed of 10 m/s at the bottom of the hill. What is its speed when it is half-way down? Assume that the track is frictionless. a . none of these b. 7.1 m/s c. 5.0 m/s d. 6.3 m/s 7. A pulley-cable system on a construction site lifts a 20,000 N concrete block to a height of 40 m. If this takes 2 minutes, what is the power of the pulley-cable system? Round your answer to the nearest whole number and include units. 8. One of the fastest and tallest roller coasters in the world is the Steel Dragon in Mie, Japan. The roller coaster has a speed of 3.0 m/s at the top of a hill. The ride includes a vertical drop of 93.5 m just after the hill. Neglecting friction, what is the speed of the riders at the bottom of the hill? Round your answer to the nearest whole number and include units. 9. How much work is done on a 6.0 kg cart to increase its speed from 2.5 m/s to 6.2 m/s? Round your answer to the nearest whole number and include units. 10. Two small toys, one with a mass of 3.2 kg and the other with a velocity of 2.4 m/s, each have the same kinetic energy of 16 J. What is the mass of the second toy? Round your answer to one decimal place and include units