Question

What will be the work done in raising the velocity of a car weighing 800 kg from 18 km/h to 54 km/h​

Answer 1

Answer:

Initial Velocity, u=54km/hr=15m/s

Final velocity , v=72km/hr=20m/s

Mass =1500kg

Initial kinetic energy

2

1

mu

2

⇒

2

1

1500×15×15=168750J

Final kinetic energy

2

1

mv

2

⇒

2

1

1500×20×20=300000J

So, change in kinetic energy = work done=300000−168750=131250J

Answer 2

Answer:

The work done in raising the velocity of a car weighing 800 kg from 18 km/h to 54 km/h​ is 8000J

Explanation:

Given,

Mass of the car (m) = 800 kg

Initial velocity of the car (u) = 18 km/hr = $18\times\frac{5}{18}$ =5 m/s

Final velocity (v)        = 54 km/hr =  $54\times\frac{5}{18}$ = 15 m/s

According to work - energy theorem,

Work done = change in kineti energy

We know,

kinetic energy (K.E) = $\frac{1}{2} \times m V^{2}$

change in kinetic energy can be written as,

Δ K.E  = $\frac{1}{2}\times m(v^{2} - u^{2} )$

          = $\frac{1}{2}\times 800\times(15^{2} - 5^{2} )$

          = 8000 J

so,

Work done will also be 8000 J

Ans :

Work done  = 8000 J