6. In his job, Martin is handed several bricks. He carries them across a yard and hands them to a bricklayer. He thinks he works hard, but his sister tells him that he does no work on the bricks. Why is his sister correct? How might he accomplish the same tasks while doing work on the bricks? 7. You have learned how kinetic energy can cause change. Give an example of how work can increaSe the kinetic energy of an object. 8. Use the formula for work done when the direction of force is at an angle to the direction of motion to show why no work is done on an object when the direction of force is perpendicular to the direction of motion. Applying Physics Knowledge Answer the followlng questions. Use complete sentences or show your colculotlons. 1. In terms of ideal mechanical advantage, what happens when you shift the gears of a multispeed bicycle? 2. A IOUN weight is raised from the ground to 1.80 m above the ground. How much work is done on the weight? 9. An adult exerts a force of 25 N to pull a child 350 m across the snow on a sled. lfthe rope that joins the sled is at an angle of 30.0\" above the horizontal, how much work is done in pulling the sled? 10. A shelf stocker lifts a 7.5kg carton from the floor to a height of 0.70 m, carries it 45 m at constant speed across the store and places it on a shelf 1.5 m above the floor. How much work does the worker do on the carton? 11. At what speed can a 120-W motor lift a ZBUO-N load? 12. A mover uses a force parallel to the ramp of 720.0 N to push a 370.0-kg piano on wheels up a ramp onto a stage. The ramp is 8.00 m long, and the stage is 1.50 m above the floor. a. How much work does the mover do on the piano? b. What is the output work ofthe ramp? A worker uses an ideal machine to lift a 15.0-N weight a distance of 4.50 m. He uses a force of IOU N. How far does the effort force move? Remember that in an ideal machine, output work is equal to input work. An effort force of 250.0 N is applied to an ideal machine. The effort force moves an 800.0-N object a distance of 280.0 cm. 1What is the mechanical advantage of the machine? It takes an electric motor 12 s to move a 450N load a distance of 25 m. How much power is developed by the motor? A machine requires a work input of 180 J to achieve a work output of 140]. What is the efficiency' of the machine? A machine lifts 240 kg a distance of 120 m in 45 5. How much power is generated bv the machine? Heidi and her mother exert a total force of 3.90x 102 N in moving a heavv sofa 14.0 m to another room. Her mother exerts twice as much force as Heidi exerts. How much work does each person do in moving the sofa