Makalu

Physics: Yadda ake lissafin screw

  • A karatunmu na kimiyya da fasaha a gefen kimiyyar lissafi (physics), yau zamu duba daya daga cikin misalan simple machine. In baku manta ba, a baya mun yi bayani akan machine da misalansu. A cikin waccan makala na kawo muku screw a matsayin misalin simple machine, a kan haka ne, a yau zamu dora akan wancan bayanin na mu ta yadda zamu duba ko ince mu koyi yadda ake lissafin screw din.

    Misalan machines da ake kira da suna screw sune:

    1. Bolts and nut
    2. Car screw jack
    3. Engineer’s vice e.t.c

    Gaba daya screw suna da thread. Nisa (distance) dake tsakanin successive thread a jikin screw ana kiransa da its pitch for one complete revolution. Shi screw yana tafiya ne mai nisa wanda yake dai-dai da its pitch.

    Hakkin mallakar hoto: notesandsketches

    Yanzu zamu ga yadda ake samo formula da ake amfani da ita wajen lissafin screw.

    Work done = work output

    Effort × distance moved by effort = load × distance moved by load.

    Effort × circumference of handle = load × pitch

    E × 2πr = L × p

    Hence , the velocity ratio

    V.R = 2πr/p

    For a perfect friction-less screw , M.A = V.R

    Hence , M.A = V.R = 2πr/p

    For a screw jack, "r" shine length na handle ko tommy bar na screw jack.

    Yanzu zamuyi amfani da wadannan fomulolin domin amsa tambayoyi wanda zamu dauko daga jarabawan karshe tagama sakandire wato WAEC.

    Tambaya ta Farko:

    1. A screw jack whose pitch is 4.4mm is used to raised a body of mass 8000kg through a height of 20cm. The length of the Tommy bar of the jack is 70cm. If the efficiency of the jack is 80%, calculate:

    1. The velocity ratio of the jack
    2. Mechanical advantage of the jack
    • Effort required in raising the body
    1. Work done by the effort in raising the body [ = 10ms-2 ; π = 22/7] (WAEC 1993)

    Amsar tambaya:

    Yanzu zamu fara fitar da abubuwan da aka bamu kafin mu fara amsa tambayoyin kai tsaye.

    Data:

    Pitch, p = 4.4mm = 0.0044m;

    Mass, m = 8000kg; g = 10m/s2

    Load, L = mg = 800 × 10 = 80000N

    Distance load moved, l = 20cm = 0.2m;

    Length of Tommy bar, r = 70cm = 0.7m;

    Efficiency, £ = 80%

    A tambayar farko an bukaci muyi lissafin velocity ratio na jack din don haka zamu yi amfani da formula mu da muka samo, ga ta kamar haka: V.R = 2πr/p

    1. The velocity ratio, V.R = 2πr/p = [ 2 × 22/7 × 0.70 ] / 0.0044 = 4.4 / 0.0044 = 1000
    2. Ana bukatar mu nemo mechanical advantage na jack, daga £ = M.A/V.R × 100% zamu samu

    Mechanical advantage, M.A = £ × V.R/100 = 80 × 1000 / 100 = 800

    • Effort required in raising the body , M.A = load/effort = L/E     Effort = L/ M.A = 80000/800 = 100N
    1. Work done by effort = work input

    Efficiency = work output /work input × 100%

    Work input = work output/efficiency × 100%

    = load × distance moved by load / efficiency × 100%

    = load × distance moved by load / efficiency ×100%

     = L × l × 100 / £ = 80000 × 0.2 × 100 / 80

    = 1600000 / 80 = 20000J = 20KJ

    Tambaya ta Biyu:

    1. A screw jack with a Tommy bar of length 12cm is used to raise a car through a vertical height of 25cm by turning the Tommy bar through 50 revolution. Calculate the approximate velocity ratio of the jack. [ π = 3.14 ] (WAEC 2001 /2014)

    Amsar tambaya:

    Data:

    Length of Tommy bar , r = 12cm;

    Number of revolution, n = 50

    Height raised or distance load moved,  h = 25cm;

    Therefore, pitch , p = h/n = 25cm / 50 = 0.5cm

    Velocity ratio, V.R = 2πr / p = 2 × 3.14 ×12cm / 0.5cm = 75.36cm / 0.5 = 150.72 approximately 151

    Wannan shine kadan daga cikin misalan yadda ake lissafin screw. Da fatan mai karatu ya karu da wannan darasin. Sai mun hadu a makala na gaba, amma kafi nan, mai karatu na iya duba makalunmu na baya, kamar:  Yadda ake lissafin inclined plane da pulley machine da makamantansu.

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