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A body of mass 2kg is released from a point 100m above the g...
waec-2019 ssce-exam-2019 waec-physics-2019 physics
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A body of mass 2kg is released from a point 100m above the ground. Calculate its kinetic energy 80m from the point of release

A. 1600J

B. 900J

C. 600J

D. 200J

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james_mark
Asked by james_markrep:742
School not set Nigeria
22 August 2020

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dp
alberteinstein
A
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dp
Timolee9, LAUTECH
Potential energy =mgh, 2×10×80=1600J
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judziy
Judziy answeredrep:2.1K
University of Benin Nigeria
22 August 2020
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Kinetic energy (K.E) = 1/2 mv2 ------------ eqn(1)

Where m is the mass and v is the velocity

from newton's third law of motion, v= u2 + 2as,

If the body/object is falling under gravity, the relation becomes:

v2 = u+ 2gh ------------- eqn(2)

Where g, acceleration due to gravity = 10m/s2 and h is the height.

Since the object (released at an initial height of 100m) falls 80m (free falling under gravity), eqn(2) can be used to find the velocity at which the body is falling.

v2 = u2 + 2(10 × 80)

Also u = 0

v2 = 02 + 1600

v= 1600

v = 40m/s

From eqn(1), K.E = 1/2 × 2 × 402

= 1600J

Answer: A

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james_mark
Thanks
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dp
Timolee9, LAUTECH
P.E =K.E=mgh
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