Question

a body of mass 2kg is released from a point 100m above the ground calculate the kinetic energy 80m from the point of release​

Answer 1

Answer:

V^2 = Vo^2 + 2g*(100-80) = 0 + 19.6*20 = 392, V = 19.8 m/s @ 80 m above gnd. KE = 0.5*M*V^2 = 0.5*2*392 = Joule

this correct answer

Answer 2

Given:

• Mass of body, m = 2 kg
• Height from which body is released = 100 m

To find:

• Kinetic energy of Body at 80 m from the point of release, K.E. =?

Formulae required:

• Third equation of motion

      2 a s = v² - u²

[ Where a is acceleration, s is distance covered, v is final velocity, u is initial velocity ]

• Formula to calculate Kinetic energy

      K.E. = 1/2 m v²

[ Where K.E. is kinetic energy, m is mass and v is velocity ]

Solution:

• Taking acceleration due to gravity, a = 10 m/s²
• Initial velocity of body, u = 0
• Distance covered by body, s = 80 m  

Using third equation of motion

→ 2 a s = v² - u²

→ 2 ( 100 ) ( 80 ) = v² - ( 0 )²

→ 1600 = v²

→ v = √1600

→ v = 40 m/s

Hence,

velocity of body after travelling 80 m would be 40 m/s.

Now,

Using formula to calculate Kinetic energy

→ K.E. = 1/2 m v²

→ K.E. = 1/2 ( 2 ) ( 40 )²

→ K.E. = 40²

→ K.E. = 1600 J

Therefore,

• Kinetic energy of body would be 1600 Joules.