Question

19. The mass of a person is 20
kg. How fast should he run so
that his kinetic energy is 1000J
?
100m/s
10m/s
1000m/s​

Answer 1

Answer:

he need to run with a seed of 10m/s

Explanation:

kinetic energy=1/2mv2

here 1000=1/2*20*v2

so 20v2=2000

so  v2=100

so  v = root 100

      =10m/s

Answer 2

Given

• Mass = 20 kg
• Kinetic Energy = 1000 J

To Find

• Velocity

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 velocity

Therefore

$\sf \longrightarrow v=\sqrt{\dfrac{2KE}{m}}$

Given that

• Mass = 20 kg
• Kinetic Energy = 1000 J

Hence

• m = 20 kg
• KE = 1000 J

Substituting the values

We get

$\sf \longrightarrow v=\sqrt{\dfrac{2 \times 1000}{20}} \ m/s$

$\sf \longrightarrow v=\sqrt{\dfrac{2000}{20}} \ m/s$

$\sf \longrightarrow v=\sqrt{\dfrac{200}{2}} \ m/s$

$\sf \longrightarrow v=\sqrt{100} \ m/s$

Therefore

$\sf \longrightarrow v=10 \ m/s$