Question

what is mass of car he moving at 90km/h with 25 KJ kinetic energy?

Answer 1

Given :-

★Velocity of car = 90km/h

★ kinetic energy (K.E) = 25 kilo jolues

To find :-

Mass of the car

$\boxed{\sf\ K.E= \dfrac{1}{2}mv^2}$

Convert velocity in m/s

$\sf \ 1km/h= \dfrac{5}{18}m/s\\ \\ : \implies\sf \cancel{90}\times \dfrac{5}{\cancel{18}}\\ \\ :\implies\sf velocity = 5\times 5= 25m/s$

• Kinetic energy

★ 1 KJ= 1000J

25kilo joules = 25000 joules

Now find the mass

$:\implies\sf K.E= \dfrac{1}{2}mv^2\\ \\ :\implies\sf 25000= \dfrac{1}{2}\times m \times (25)^2\\ \\ :\implies\sf 25000\times 2 = m\times 625\\ \\ :\implies\sf 50,000= 625m\\ \\ :\implies\sf \cancel{\dfrac{50000}{625}}= m\\ \\ :\implies\sf 80 = m \\ \\ :\implies\sf Mass = 80kg$

$\underline{\boxed{\sf{\ MASS\ OF \ CAR = 80kg}}}$

Answer 2

In the above Question , the following information is given -

The car is moving at a velocity of 90 kmph .

It has a kinetic energy of 25 kilo Joules .

Here , we have to find the mass of the car .

Solution -

We know that -

$\sf{\boxed{\boxed { Kinetic \: Energy \: = \: \dfrac{1}{2} m v^2 }}}$

Now , let us assume that the mass of the car is X .

Velocity Of Car = 90 kmph = 90 × ( 5 / 18 ) m/s

=> Velocity Of the car = 25 m/s.

Kinetic Energy of the car = 25 KJ

=> 25000 Joules

Substituting the given Values -

$\sf {\therefore{ \dfrac{x}{2} \times 625 = 25000 }} \\ \\ \sf{ \purple{ \leadsto { X = 80 kg }}}$

Hence the required Mass of the car is 80 kg .