1 Ruth is moving a heavy box a distance of 14 m across the floor of her bedroom. If she does 9000 J of work in 3 s, her power is _____. 3000 W 12000 W 149 W 1500 W 2 points QUESTION 2 The rate at which work is done is equivalent to: increase in potential energy thermal energy potential energy power 2 points QUESTION 3 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? 6.67 kW 3.34 kW 13.3 kW 400 kW 2 points QUESTION 4 A jet engine is moving an airplane forward at a speed of 900 km/hr. If the thrust of the engine is 1 x 105 N, what is the power developed by the engine? 5 MW 10 MW 25 MW 50 MW 2 points QUESTION 5 For safety reasons, the speed of a child at the bottom of a playground slide cannot exceed 6.0 m/s. What is the maximum height of the slide? 1.8 m 2.9 m 3.2 m 4.5 m 2 points QUESTION 6 Sarah and her bicycle have a total mass of 40 kg. Her speed at the top of a 10 m high and 100 m long hill is 5 m/s. If the force of friction on her way down is 20 N, at what speed will she be going when she reaches the bottom? 5 m/s 10 m/s 11 m/s She stops before she reaches the bottom 2 points QUESTION 7 A boy on a roof throws one ball downward and an identical ball upward. The ball thrown downward hits the ground with 100 J of kinetic energy. If both balls are thrown at the same speed and there is no air friction, what is the kinetic energy of the second just before it hits the ground? 100 J 200 J Less than 100 J More than 200 J none of the above 2 points QUESTION 8 A 0.145 kg rock is thrown with a speed of 32.0 m/s at an angle of 40. What is its kinetic energy at the top of its trajectory? 43.6 J 74.2 J 30.6 J 13.0 J 2 points QUESTION 9 A rubber ball is dropped on the floor. The rebound speed is one-half the speed it had just before hitting the floor. It will rise to ________ of the original height from which it was dropped. 1/8 1/6 1/5 1/4 1/3 2 points QUESTION 10 A 500 kg roller coaster car crests a 20 m high hill at a speed of 10 m/s. It then rolls down the other side, all the way to ground level, and climbs a second hill. What is the speed of the car when it is 10 m up the second hill? 15.3 m/s 17.2 m/s 8.90 m/s 19.7 m/s 2 points QUESTION 11 A pendulum, 2.0 m in length, is released with a push when the string is at an angle of 25 from the vertical. If the initial speed of the pendulum is 1.2 m/s, what is its speed at the bottom of the swing? 2.3 m/s 2.6 m/s 2.0 m/s 0.5 m/s 2 points QUESTION 12 A 1.5 kg object falls from a height of 2.0 m onto a spring scale with a spring constant of 1.5x105 N/m. What is the reading on the scale at its greatest compression? 15 N 30 N 1.5 x 103 N 2.1 x 103 N 3.0 x 103 N 2 points QUESTION 13 An object is thrown vertically upward with an initial kinetic energy of 4000 J from the level where its potential energy is 6000 J. When it is halfway to its highest point, its kinetic energy will be _____ J and its potential energy will be ______ J. 6000, 4000 2000, 3000 2000, 4000 2000, 8000 2 points QUESTION 14 A 0.20 kg particle moves along the x axis. The potential energy is given by U(x) = 8x2 + 2x2. If the particle has a speed of 5.0 m/s when it is at x = 1.0 m, its speed when it is at the origin is: 0.0 m/s 2.5 m/s 5.7 m/s 7.9 m/s 11 m/s