Multiple Choice - Weebly



Practice: PowerMultiple ChoiceA construction laborer holds a 20 kg sheet of wallboard 3 m above the floor for 4 seconds. During these 4 seconds how much power was expended on the wallboard?2400 W (B) 340 W (C) 27 W (D) 15 W (E) none of theseP = Fd / t. Since there is no distance moved, the power is zero If M represents units of mass, L represents units of length, and T represents units of time, the dimensions of power would be:Answer: CAn automobile engine delivers 24000 watts of power to a car’s driving wheels. If the car maintains a constant speed of 30 m/s, what is the magnitude of the retarding force acting on the car?800 N (B) 960 N (C) 1950 N (D) 720,000 N (E) 1,560,000 004P = Fv, plug in to get the pushing force F and since its constant speed, Fpush = fk A constant force of 900 N pushes a 100 kg mass up the inclined plane shown at a uniform speed of 4 m/s. The power developed by the 900 N force is most nearly(A) 400 W(B) 800 W(C) 900 W(D) 1000W(E) 3600 WSimple P = Fv A horizontal force F is used to pull a 5-kilogram block across a floor at a constant speed of 3 meters per second. The frictional force between the block and the floor is 10 newtons. The work done by the force F in 1 minute is most nearly0 J (B) 30 J (C) 600 J (D) 1,350 J (E) 1,800 JSince the speed is constant, the pushing force F must equal the friction force (10 N). Thedistance traveled is found by using d = vt = (3)(60 sec), and then the work is simply foundusing W=Fd A weight lifter lifts a mass m at constant speed to a height h in time t. What is the average power output of the weight lifter?mg (B) mh (C) mgh (D) mght (E) mgh /tThe force needed to lift something at a constant speed is equal to the object weight F=mg. Thepower is then found by P = Fd / t = mgh / tFree ResponseProblem 2C1990M2. A block of mass m slides up the incline shown above with an initial speed voa. If the incline is frictionless, determine the maximum height H to which the block will rise, in terms of the givenquantities and appropriate constants.in the position shown.b. If the incline is rough with coefficient of sliding friction μ, the box slides a distance d = h2 / sin θ along thelength of the ramp as it reaches a new maximum height h2. Determine the new maximum height h2 in terms ofthe given quantities.SolutionProblem 21974B7. A ski lift carries skiers along a 600 meter slope inclined at 30°. To lift a single rider, it is necessary tomove 70 kg of mass to the top of the lift. Under maximum load conditions, six riders per minute arrive at thetop. If 60 percent of the energy supplied by the motor goes to overcoming friction, what average power mustthe motor supply?Solution ................
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