Question

If the mass of a car is 3 quintals and it is running at a speed of 100km/h and it increases its speed to 120km/h then find the work done by car engine. ​

Answer 1

Given:

• A car of 3 quintal is running at a speed of 100km/hr.
• It increases its speed to 120km/hr.

To Find:

• The work done by the car.

Answer:

Mass of car = 3 quintal = 3×100 kg = 300kg. (m)

Initial speed of car = 100km/hr. (u)

Final speed of car = 120km/hr . (v)

Converting speed in SI units ,

☞u = 100km/hr = 100×5/18m/s

= 27.77m/s = 28m/s. (approx)

☞ v = 120km/hr = 120×5/18 m/s

= 33.33m/s = 33m/s ( approx)

Now , we can use here "Work Energy Theorem " to find the work done , which is stated as ;

$\large{\underline{\boxed{\red{\bf{\leadsto Work\:done = \Delta Kinetic\: Energy }}}}}$.

⇒Work = ∆ K . E .

⇒Work = ½ mv² - ½ mu² .

⇒Work = ½m ( v² - u² ).

⇒Work = ½ m [ (33 m/s)² - (28 m/s)² ].

⇒ Work = ½ m [ 1089 m²/s² - 784 m²/s²]

⇒ Work = ½ × 300 kg × 305 m²/s².

☞ Work = 45750 J .

Hence the work done is 45,750 Joules.