A weight lifter picks up a barbell and lifts it chest high,holds it for 5 minutes,puts it down………..?

1. A weight lifter picks up a barbell and lifts it chest high,holds it for 5 minutes,puts it down. Rank the amounts of work W the weight lifter performs during this three operations. Label the quantities as W1, W2, and W3. Justify you ranking order.

2. Estimate the amount of work the engine performed on a 1200 kg car as it accelerated at 1.2 m/s2 over a 150 meter distance.

3.A real world roller-coaster released at point A and coasting without external power would traverse a track somewhat like the figure above. Friction is not negligible in the real world. If we call the potential energy at point A relative to the ground Uo what can you say about the potential and kinetic energies UB, UB at point B and the potential and kinetic energies UC, UC at point C.

Update:

4. A gallon of gasoline contains about 1.3 x 108 joules of energy. A 2000 kg car traveling at 20 m/s skids to a stop. Estimate how much gasoline it will take to bring the car back to the original speed? To complicate matters further, consider the fact that only about 15% of the energy extracted from gasoline actually propels the car. The rest gets exhausted as heat and unburnt fuel.

4. A gallon of gasoline contains about 1.3 x 108 joules of energy. A 2000 kg car traveling at 20 m/s skids to a stop. Estimate how much gasoline it will take to bring the car back to the original speed? To complicate matters further, consider the fact that only about 15% of the energy extracted from gasoline actually propels the car. The rest gets exhausted as heat and unburnt fuel.

2 answers by real people - A weight lifter picks up a barbell and lifts it chest high,holds it for 5 minutes,puts it down………..?

  • 1 month ago

    i am not sure if these are right or not but i got…….which would be w1

    holding has 0 work due to the fact that their is not a change in x so x=0 thus the calculation would be 0. so that is w3 then w2 is puting wait down

    others may argue that puttin weight down in negative so it should be last but i think theoretically that since it has a number it is still greater than 0

    f= 1200kg*1.2m/s^2=1440

    d=150m

    w=fdcos0= fd

    1440*150=216000J

    well at ub kinetic and potential energy are the same at 50-50 due to the fact that the hill is about half the size of A. point c id say potential energy is about 25% while kinetic is about 75% since its a lot lower than point A

  • Vince P.
    1 month ago

    12.34 k/cal

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