Question

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

Answer 1

ㅤ$\;\;\underline{\textbf{\textsf{Given:-}}}$

• Velocity of car = 90km/h

( Converting velocity km/h into m/s)

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

• Kinetic Energy (K.E) = 25 kilo joules or

25000 joules

ㅤ$\;\;\underline{\textbf{\textsf{To Find :-}}}$

• Mass, m

ㅤ$\;\;\underline{\textbf{\textsf{Solution :-}}}$

$\underline{\:\textsf{ As we know that :}}$

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

$\underline{\:\textsf{ Putting the given values :}}$

$\dashrightarrow \sf 25000= \dfrac{1}{2}\times m \times (25)^2\\ \\ \dashrightarrow \sf 25000\times 2 = m\times 625\\ \\ \dashrightarrow \sf 50,000= 625m\\ \\ \dashrightarrow \sf \cancel{\dfrac{50000}{625}}= m\\ \\ \dashrightarrow \sf 80 = m \\ \\ \dashrightarrow \sf Mass = 80kg$

ㅤ$\;\;\underline{\textbf{\textsf{ Hence-}}}$

$\underline{\textsf{ Mass of car is </p><p>\textbf{ 80 kg}}}.$

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Answer 2

Answer:

★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}

K.E=

2

1

mv

2

Convert velocity in m/s

\begin{gathered}\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\end{gathered}

1km/h=

18

5

m/s

:⟹

90

×

18

5

:⟹velocity=5×5=25m/s

Kinetic energy

★ 1 KJ= 1000J

25kilo joules = 25000 joules

Now find the mass

\begin{gathered}:\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\end{gathered}

:⟹K.E=

2

1

mv

2

:⟹25000=

2

1

×m×(25)

2

:⟹25000×2=m×625

:⟹50,000=625m

:⟹

625

50000

=m

:⟹80=m

:⟹Mass=80kg

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

MASS OF CAR=80kg