A brick of mass 2 kg is dropped from a height of 5 m above the ground. What is its velocity at a height of 3 m above the ground?
Answers
Answer:
4 ithink answer is right
Answer:
The velocity of the brick at a height of 3 m above the ground is 6.3 m/s.
Explanation:
The mass of the brick, m = 2 Kg
The acceleration acting on the brick, g = 9.8 m/s²
The height of the brick from ground level before dropping, h = 5 m
The potential energy at this height, P.E = mgh
= 2 × 9.8 × 5
= 98 J
By the law of conservation of energy, the sum of kinetic and potential energies must be a constant. ie; the sum of kinetic and potential energies will always be 98 J.
At maximum height:
Kinetic energy will be zero.
K.E + P.E = 98 J
0 + 98 = 98 J
At a height of 3 m above the ground level:
K.E + P.E = 98 J
(mv²) / 2 + mgh = 98
(2 × v²) / 2 + (2 × 9.8 × 3) = 98
v² + 58.8 = 98
v² = 98 - 58.8
v² = 39.2
∴ v = 6.3 m/s