A constant external force P = 310 N is applied at an angle 30° below the horizontal to a 20 kg box, pushing the box across a horizontal frictionless surface. If it started at rest, what is the box’s kinetic energy after it has been pushed 8.0 m?

A box of mass 4.0 kg hangs by a cable from the ceiling of an elevator. The elevator is moving down at a steady speed of 5.0 m/s for 8.0 m. Use g = 10 m/s2. Match the answers with questions. m v the final kinetic energy of the box (Kf) А. -320 J v the change in kinetic energy of the box (AK) В. 20 J C. 320 J D. 50 J E. -20 J F. -50 J G. OJ

What is the minimum amount of work needed to lift a 3 kg box 2 meters? a. 60 J b. 5 J c. 15 J d. 120 J e. 180 J

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Question 23 A 5.0-kg block that initially has a speed of 6.0 m/s is moving in a straight line on a level surface where there is kinetic friction between the block and the surface. What is the magnitude of the work done by the frictional force after the block comes to rest? O out of 4 points Answers: a, 210 J b. 120 J c. 150 J d. 90 J e. 180 J

A block of mass 2.28 kg starts sliding from rest down an incline plane for 25 cm. If the block has a velocity of 1.14 m/s, and the incline has an angle measured from the +x axis of 37 degrees then: a. How much work did kinetic friction do on the block? b. What is the coefficient of kinetic friction between the block and the incline?

A 290-kg piano slides 4.2 m down a 35˚ unloading ramp. A man is pushing back on the piano with the force of 820 N at the angle of 20˚ below the plane of the ramp, so that the piano's slide proceeds at constant velocity. Find the work of friction during the slides. a. 2500 J b. -2500 J c. 3600 J d. -3600 J

You do 30 J of work to load a toy dart gun. However, the dart is 10 cm long and feels a frictional force of 10 N while going through the dart gun’s barrel. What is the kinetic energy of the fired dart?  a. 30 J b. 29 J c. 28 J d. 27 J

A 500 kg cart rests atop a hill 30.0 m high on a roller coaster. Its gravitational potential energy is measured relative to the bottom of the hill. The cart then rolls down the hill. Which of these best describes what is happening in this situation?   a. the total mechanical energy of the cart is decreasing, the kinetic energy of the cart is increasing, and the gravitational potential energy of the cart is increasing   b. the total mechanical energy of the cart is increasing, the kinetic energy of the cart is increasing, and the gravitational potential energy of the cart is increasing   c. the total mechanical energy of the cart is increasing, the kinetic energy of the cart is increasing, and the gravitational potential energy of the cart is decreasing   d. the total mechanical energy of the cart is increasing, the kinetic energy of the cart is decreasing, and the gravitational potential energy of the cart is increasing   e. the total mechanical energy of…

39 A 1.00 kg block slides down a 20.0 meter ramp at a constant velocity. The angle of inclination of the ramp is 30°. How much work is done by friction? Ans. 98.0 J 45. A car pulls a trailer with a force of 2000 N at 20.0 m/s. What is the Ans. 4.00 x 104 Watts power exerted?