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Physics help PLEASE I cant fail!!!?

Physics is the hardest subject for me I just can't ever understand it. If you want to email me the answers that's fine too, my email is ashtenmccomb@yahoo.com I really need help ):

1.A 500.0 g metal block absorbs 1.125 × 104 J of heat to raise its temperature by 50.0 K. What is the substance?

Show your work.

Specific Heats of Selected Substances

Substance C [J/(kg•K)]

Water (ice) 2,060

Iron 450

Aluminum 897

Gold 130

Copper 385

Silver 235

Ammonia (liquid) 4,700

Water (liquid) 4,180

Water (steam) 2,020

Lead 128

2. A 5.0 Ω resistor is hooked up in series with a 10.0 Ω resistor followed by a 20.0 Ω resistor. The circuit is powered by a 9.0 V battery.

a.) Draw a labeled circuit diagram for the circuit described using correct symbols.

b.) Calculate the equivalent resistance.

c.) Calculate the voltage drop across each resistor in the circuit.

3.A man lifts various loads with the same lever. The distance of the applied force from the fulcrum is 1.00 m, and the distance from the fulcrum to the load is 0.250 m. A graph of resistive force vs. effort force is shown. What is the mechanical advantage of the lever?

What is the ideal mechanical advantage of the lever? What is the efficiency of the lever? Show your work

4.An 800.0 kg roller coaster car is at rest at the top of a 95 m hill. It rolls down the first drop to a height of 31 m. When it travels to the

1 Answer

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  • oubaas
    Lv 7
    7 years ago

    1. A 500.0 g metal block absorbs 1.125 × 104 J of heat to raise its temperature by 50.0 K. What is the substance?

    Q = c*m*ΔT

    1.125*10^4 = c*0.500*50

    c = 1.125*10^4/25 = 450 J/kg/K....i dare say we are talking about iron !!!!

    2) A 5.0 Ω resistor R3 is hooked up in series with a 10.0 Ω resistor R1 followed by a 20.0 Ω resistor R2. The circuit is powered by a 9.0 V battery.

    a.) Draw a labeled circuit diagram for the circuit described using correct symbols.

    see below

    b.) Calculate the equivalent resistance.

    Re = R1+R2+R3 = 10+20+5 = 35 ohm

    c.) Calculate the voltage drop across each resistor in the circuit.

    Vr1 = V*R1/Re = 9*10/35 = 2.57 V

    Vr2 = V*R2/Re = 9*20/35 = 5.14V

    Vr3 = V*R3/Re = 9*5/35 = 1.29 V

    3)

    A man lifts various loads with the same lever. The distance of the applied force from the fulcrum is 1.00 m, and the distance from the fulcrum to the load is 0.250 m. A graph of resistive force vs. effort force is shown.

    What is the mechanical advantage of the lever?

    k = 1.00/0.25 = 4.00 the applied force is 1/4 of the loads to lift

    What is the ideal mechanical advantage of the lever?

    infinitive !!!

    What is the efficiency of the lever?

    Eff.cy properly said cant be higher than 1 !!!

    if we consider the work done (force multiplied by displacement) we discover that the work done to the load is equal to the work done on the lever ...the eff.cy is 1.00 !!!

    4) An 800.0 kg roller coaster car is at rest at the top of a 95 m hill. It rolls down the first drop to a height of 31 m. When it travels to the.....

    Uo = m*g*ho = 800*10*95/1000 = 760.00 kjoule

    U1 = m*g*h1 = 800*10*31/1000 = 248.00 kjoule

    V1 = √2(Uo-U1)/m = 35.78 m/sec ( 129 kmph ; 80 mph)

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