## Physics: Me ku ka sani game da work, da energy da kuma power?

• A karkashin ilmin kimiyyar lissafi wato (physics) yau zamu yi karatu ne akan wasu abubuwa masu mahimmanci a rayuwarmu ta yau da kullum wanda ako yaushe cikinsu muke. Wadannan abubuwa gas u kamar haka:

1. Work
2. Energy
3. Power

Wadannan abubuwan kamar yadda na fada da su muke rayuwa a yau da kullum. Zan kawo takaitattun bayanai akansu sannan mu ga yadda ake lissafinsu ta hanyar amsa tambayoyi.

Work:

Idan aka ce work wato aiki kenan a Hausance. Zamu iya daukar misalai kamar haka daban-daban don nuni ga ma’anar wannan Kalmar; wani mutum yana noma, dalibi yana karatun jarabawa, magini yana kwasar bullo, duk wadannan misalai ne na aiki.

Amma a karkashin ilmin kimiyyar lissafi (physics) kalmar work tana nufin wani abu mai ma’ana wanda yana kebance ne, kamar misali mutumin da yake da karfin yin aiki na sa’o’i shidda ko bakwai a rana ana cewa yana da large stamina ko energy. Idan zamu duba karatukan da muka yi dangane da vectors wanda mun yi bayani sosai da kuma lissafinsu, zai taimaka wajen samun saukin fahimta lissafin work.

A Turance akanyi bayanin work ne kamar haka:

Work is defined as the product of a force and the distance in the direction of the force.

Work done,W = force × distance (displacement)

W = F × s, ko kuma W = mg × s

However, if the applied force applied at an angle ? to the horizontal kamar yadda aka nuna a zanen daya zo fig 1. 0. the work done depends on what direction the objects moves. Fig 1.0

If the bpx moves in the horizontal direction, the work done is;

W = F cos? × s ko kuma, W = mg cos?× s

Idan kuma box din yana tafiya ne a vertical direction, the work done is;

W = F sin? × s ko kuma

W = mg sin? × s

Where

F = Force in Newton S = distance or displacement in meter, m

m = mass in kilogram, kg

g = acceleration due to gravity, m/s2

ana measuring work ne da Joules.

Energy

A karkashin ilmin kimiyyar lissafi a Turance ana bayanin energy ne kamar haka: Energy is the capacity to do work. Energy ya rabu biyu sune, kinetic energy (K.E) da potential energy (P.E).

1. Kinetic energy (KE) is the energy possessed by a body in motion. KE = ½ mv2
2. Potential energy is the energy possessed by a body at rest or at a heaight. PE = mgh

Where

v = velocity in meter per second, m/s

g = acceleration due to gravity, m/s2

h = height in meter (m)

Power

Wannan kalmar ta power ana amfani da ita a kullum kuma ta hanyar ma’anoni daban-daban yana da kyau mu gane akwai banbancin ma’ana physical da psychological. A kimiyance ma’anar power cikin harshen Turanci gas hi kamar haka;

power is defined as the rate of doing work or the rate of energy transfer.

Power = work done /time taken (t)

= force × distance / time taken = Force × distance / time = Force × Velocity

P = W / t = F × s / t = mg × s / t = F × v

Power is measured in Joules per second (J/s) ko kuma watts horsepower (hp) = 746W = 0.746W.

Yanzu zamu dauki misalai wanda suke fitowa a jarabawar karshen gama sakandire dominmu amsa tambayoyin.

Misali na daya (work)

A boy drags bag of rice along a smooth horizontal floor with a force of 2N applied at an angle 600 to the floor. The work done after a distance of 3m is. A. 6J   B. 3J   C. 4J D. 5J (JAMB 2007)

Amsar Tambaya

Force F = 2N; ?= 600; distance = 3m

Work done = F cos?× s

= 2 cos60 × 3

= 2 × 0.5 × 3 = 3J

Misali na biyu (work)

A constant force of 40N acting on a body initially at rest gives an acceleration of 0.1m/sfor 4s. Calculate the work done by the force. A.  8J B. 10J C. 32J D.  160J (JAMB 1987)

Amsar tambaya

Abubuwan da aka bamu sune; Force, F = 40N; initial velocity, u = 0; acceleration, a = 0.1m/s2; time, t = 4s.

Distance, s is obtained from second equation of motion,

s = ut + 1/2at

s = 0 × 4 + ½ × 0.1 × 42

s = 0 + 0.05 × 16

s = 0.8m

work done = F × s = 40 × 0.8 = 32J.

Za a iya duba: Physics linear momentum

Misali na uku (power)

An engine raises 100kg of water through a height of 60m ins 20s. what is the power of the engine? Take g = 10m/s(WAEC 1989)

Amsar tambaya

An bamu; mass, m = 100kg; g = 10m/s; distance , s = 60m; time, t = 20s

Power = work done (w) / time taken (s)= force × distance / time taken = mg × s / t

P = mg × s / t = 100 × 10 × 60 / 20 = 3000W.

Misali na hudu (power)

The engine of a train produces a force of 3000N when moving at 30m/s. calculate the power of the engine of the engine. WAEC 2006

Amsar tambaya

Given: force = 3000N; speed = 30m/s

Power = Force × Distance / time taken [ speed = distance / time]

P = force × speed (velocity)

P = 3000N × 30m/s = 90000 = 9.0 × 104W

Misali na biyar (power)

A car of mass 800kg attains a speed of 25ms-1 in 20 seconds. The power developed in the engine is A.  1.25 × 10 4 W B. 2.50 10W C.1.25 ×10W D. 2.50×106W  JAMB 1999

Amsar tambaya

Data

Mass, m = 800kg; speed velocity, v = 25ms-1; time, t = 20s.

Acceleration, a = velocity / time = 25 / 20 = 1.25m/s

Force, F = ma = 800 × 1.25 = 1000N

Power, P = Force × Velocity = 1000 × 25

= 25000W or 25KW

Misali na shida (force)

A body of mass 4kg is acted on by a constant force of 12N for 3seconds. The kinetic energy gained by the body at the end of the time is. A .162J B. 144J C.72J D.81J; JAMB 2004

Amsar tambaya

Mass, m = 4kg; Force, F = 12N; time, t = 3s

F = ma,

Therefore, acceleration, a = F / m = 12 /4 = 3m/s2

Also, acceleration, a = F/m = 12 / 4 = 3m/s2

Also, acceleration, a = velocity (v) / time (t):- Velocity , v = a × t

= 3m / s× 3s = 9m/s

Therefore, KE = ½ mv= ½ ×4 × 9= 162J.

Misali na bakwai (force)

A ball of mass 200g falls from a height of 5m on to a hard floor and rebounds to a height of 3m. what energy is lost by the ball as a result of the impact on the floor [ g= 10ms-2]   NECO 2006.

Given: mass, m = 200g = 0.2kg; g = 10m/s2

Potential energy at height, h = 5m,

PE= mgh = 0.2 × 10 × 5

=10J

Potential energy at height, h = 3m, PE= mgh

0.2 × 10 × 3 = 6J

Energy lost = PE– PE= 10 – 6 = 4J

Wadannan sune kadan daga cikin abubuwan da ya kamata musani game da work, da energy da kuma power. Kuma kamar yadda na ke fadi a kullum, yana da kyau dalibai su kara karatu don fahimtar wannan maudu’in da kyau da kuma wasu maudu'an na daban.