Question

What is mass of car which is moving at 90km/h with 25 KJ kinetic energy?
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Answer 1

Given :-

• $\bf\red{Velocity \ of \ car \ = \ 90km/h}$
• $\bf\orange{Kinetic \ energy \ (K.E) \ = \ 25 KJ}$

To find :-

• $\bf\green{Mass \ of \ the \ car}$

Solution :-

★ Firstly, Converting velocity in m/s

$\to\:\:\sf{1km/h= \dfrac{5}{18}m/s}$

$\to\:\:\sf{90 \times \dfrac{5}{18}}$

$\to\:\:\sf{5 \times 5}$

$\to\:\:\sf{25m/s}$

★ As we know that

• 1KJ = 1000J
• 25KJ = 25000J

★ Now, Finding the mass of car

$\to\:\:{\boxed{\bf{\purple{K.E= \dfrac{1}{2}mv^2}}}}$

$\to\:\:\sf{25000= \dfrac{1}{2}\times m \times (25)^2}$

$\to\:\:\sf{25000\times 2 = m\times 625}$

$\to\:\:\sf{50000= 625m}$

$\to\:\:\sf{\dfrac{50000}{625} = m}$

$\to\:\:\sf{80 = m}$

$\star\:{\underline{\boxed{\bf{\red{Mass\ of \ car = 80kg}}}}}$