Question

Kinetic energy of a 500 kg car travelling at 72km/h

Answer 1

Given

• Mass = 500 kg
• Velocity = 72 km/h

To Find

• Kinetic Energy

Solution

We know that

$\sf \longrightarrow KE=\dfrac{1}{2}mv^{2}$

Here

• KE = Kinetic Energy
• m = Mass
• v = Velocity

Units

• KE = Joule (J)
• m = kilogram (kg)
• v = metre/second (m/s)

According to the question

We are asked to find the kinetic energy

Therefore

We must find "KE"

Given that

• Mass = 500 kg
• Velocity = 72 km/h

Hence

• m = 500 kg
• v = 72 km/h = 20 m/s

Substituting the values

We get

$\sf \longrightarrow KE=\dfrac{1}{2} \times 500 \times 20^{2} \ J$

$\sf \longrightarrow KE=\dfrac{1}{2} \times 500 \times 400 \ J$

$\sf \longrightarrow KE=\dfrac{1}{2} \times 200000 \ J$

Therefore

$\sf \longrightarrow KE=100000 \ J$

Hence

Kinetic Energy = 100000 J

Answer 2

Answer:

Correct Question :-

• A mass of a car is 500 kg and its travelling at 72 km/h. Calculate what is the kinetic energy.

Given :-

• A mass of a car is 500 kg and its travelling at 72 km/h.

To Find :-

• What is the kinetic energy.

Formula Used :-

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

where,

• m = Mass
• v = Velocity

Solution :-

Given :

• Mass = 500 kg
• Velocity = 72 km/h = $\sf 72 \times \dfrac{5}{18}$ = 20 m/s

According to the question by using the formula we get,

⇒ $\sf Kinetic\: energy\: =\: \dfrac{1}{2} \times 500 \times {(20)}^{2}$

⇒ $\sf Kinetic\: energy\: =\: \dfrac{1}{2} \times 500 \times 400$

⇒ $\sf Kinetic\: energy\: =\: \dfrac{1}{\cancel{2}} \times {\cancel{500}} \times 400$

⇒ $\sf Kinetic\: energy\: =\: 250 \times 400$

➠ $\sf\bold{\red{Kinetic\: energy\: =\: 100000\: J}}$

$\therefore$ The kinetic energy of a car is 100000 J .