Answer :
The mass of the rock is 2.21 kg and the collision of the ground and the rock is an inelastic collision.
The height of the rock is 2 meters.
The momentum of the rock is 14 kgm/s.
We know, from the conservation of energy law, according to this the energy is always conserved,
Energy at top = energy at bottom
Only potential energy at the top = Only kinetic energy at the bottom
MgH = 1.2Mv²
Where,
M is the mass of the rock,
v is the speed of the rock at the bottom,
g is acceleration due to gravity,
H is the height of the rock.
v = √(2gH)
So, putting the values,
v = √(2x10x2)
v = 6.32 m/s.
(b) The momentum at the bottom, is given to be 14 kgm/s
Momentum = mass x velocity at bottom
Putting all the values,
14 = mass x 6.32
Mass = 2.21 Kg.
(c) This collision is inelastic.
On hitting the ground, a part of the energy of the rock will be transferred into the ground and the because the energy is not conserved. The collision is Inelastic.
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