Question

Solve the following problems: (only for genius)

1) Calculate the kinetic energy of a girl of mass 25kg running at a velocity of 3m/s.

2) A car's velocity increases from 36km/h to 72km/h . The car weighs 1400kg. Calculate the work done by the engine.

3) Calculate the potential energy of a stone of mass 500g raised to a height of 12m above the ground. Assume that acceleration due to gravity g= 10m/s²

Give the correct answer, I will mark u as branliest. ​

Answer 1

1} v = 3m/s and m= 25kg

Kinetic Energy = ½ m v²

= ½ x 25 x 3 x 3

= 112.5 Joule

2} Initial velocity = 36 km/h = 10 m/s

mass = 1400 kg

Kinetic Energy Initial = ½ x 10 x 10 x 1400

= 70000 Joule = 70 KJ

Similarly....

Final velocity = 72 km/h = 20 m/s

Kinetic Energy Final = ½ x 20 x 20 x 1400

= 280000 Joule = 280 KJ

Work Done = K.E Final - K.E Initial

= 280 KJ - 70 KJ

= 210 KJ

3} Mass = 500g = 0.5 kg

Height = 12m

g = 10m/s²

Potential Energy = mgh

= 0.5 x 12 x 10

= 60 Joule

Hope you find it helpful..

Please mark as Brainliest..

Answer 2

Explanation:

Question 1 :-

Calculate the kinetic energy of a girl of mass 25kg running at a velocity of 3m/s.

Solution 1 :-

Mass = 25 Kg

Velocity (v) = 3 m/s

Kinetic energy (K.E) = 1/2 × mv²

⇛ 1/2 × 25 × 3

⇛ 37.5 J is the kinetic energy.

Question 2 :-

A car's velocity increases from 36km/h to 72km/h. The car weighs 1400kg. Calculate the work done by the engine.

Solution 2 :-

Initial velocity (u) = 36 Km/h

Final velocity (v) = 72 Km/h

Mass (m) = 1400 Kg

》Initial velocity :

• 36 × 5/18
• 10 m/s

》Final velocity :

• 72 × 5/18
• 20 m/s

》Work done :

Change in kinetic energy.

⇒ 1/2 mv² - 1/2 mu²

⇒ 1/2 m(v² - u²)

⇒ 1/2 × 1400(20² - 10²)

⇒ 700 × (400 - 100)

⇒ 700 × 300

⇒ 210000 J is the work done.

Question 3 :-

Calculate the potential energy of a stone of mass 500g raised to a height of 12m above the ground. Assume that acceleration due to gravity g= 10m/s².

Solution 3 :-

Mass (m) = 500 g

Height (h) = 12 m

Acceleration due to gravity (g) = 10 m/s²

Potential energy = mgh

Where we have,

• m = mass
• g = acceleration due to gravity
• h = height

Substituting the values,

⇒ m = 500g = 500/1000 = 0.5 Kg

⇒ h = 12 m

⇒ g = 10 m/s²

• mgh
• 0.5 × 10 × 12
• 5 × 12
• 60 J

∴ 60 J is the potential energy.