al physic mc

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please solve the above mc with explanation

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  • 天同
    Lv 7
    9 年前
    最愛解答

    43. Hear produced = (3.1x10^17).(50x10^3).(1.6x10^-19).(0.995) w

    = 2,468 w

    Answer is Option D

    44. No. of years = 1600x[-log(0.03)/log(2)] = 8,094

    Answer is option C

    14. fo = 1/(4x10^-3) Hz = 250 Hz

    f -fo = 1/(5x25x10^-3) Hz = 8 Hz

    hence, f = (8+250) Hz = 258 Hz

    Answer is option D

    35. Period of sine-wave = (M+L) = 1/50 s = 0.02 s

    But L = 0.02/4 - (30/90).(0.02/4) s = 0.00333 s

    Hence, M = (0.02 - 0.00333) s = 0.01667 s = 16.7 ms

    Answer is option D 29. Voltage across R = 0.2x15 v = 3 vvoltage across motor = (9-3) v = 6vPower = w.v = 6x0.2 watts = 1.2 wattsNew power = 3w.(0.5v) = 1.5w.v = 1.5x1.2 watts = 1.8 wattsSince speed of raising the load is reduced by half, voltage across motor = 3 vNew current = 1.8/ 3 A = 0.6 A New resistance = (9-3)/0.6 ohms = 10 ohmsAnswer is option A 23. Option CTry tracing the light ray for angles of incident = 0 degree and 90 degrees. 4. Speed of 0.2 kg disc before sliding onto the 1 kg block = square-root[2gx1.8] m/s = 6 m /shence, final speed of the disc and block = 0.2x6/(0.2+1) m/s = 1 m /sChange of kinetic energy = (1/2).(0.2).(6^2) - (1/2).(1.2).1^2 J = 3 Jdistance travelled = 3/ 1.2 m = 2.5 m Answer is option A 17. 1.5x8x10^-6.sin(a)=3.5x6x10^-7 where a is the angular position of the 4th minimumhence a = 10.08 degreesRefracted angle in air = arc-sin[1.5.sin(10.08)] = 15.22 degreesHence, distance from O = 25.tan(10.08) + 10.tan(15.22) cm = 7.16 cm Answer is option A 40. qE = mv^2/RKE = (1/2).mv^2 = qE.R/2 = constantAnswer is option B 42. Option AFrom curve A, the highest electron energy is 2.5 eV. The work function must be lower than 2.5 eV 5. F be the frictional force and T be the tensionF - T = 2.5x0.1x4.8^2T+F = 2.3x0.2x4.8^2adding: 2F =17.28 NF = 8.64 NOption D 6. 0.4x 2.5g - T = 2.5x0.1w^2T+0.4x 2.5g = 2.5x0.2w^2dividing and solve for T gives T = 3.33 NOption B 56. Option D

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