The speed of the rock at 20 m is 34.3 m/s
Explanation:
We can solve this problem by using the law of conservation of energy: the mechanical energy of the rock, sum of its potential energy + its kinetic energy) must be conserved in absence of air resistance. So we can write:
where
:
is the initial potential energy
is the initial kinetic energy
is the final potential energy
is the final kinetic energy
The equation can also be rewritten as follows:
where:
m = 100 kg is the mass of the rock
is the acceleration of gravity
is the initial height
u = 0 is the initial speed (the rock starts at rest)
is the final height of the rock
v is the final speed when h = 20 m
And solving for v, we find:
Learn more about kinetic energy and potential energy here:
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Answer:
d. 0.3 N
Explanation:
Force: This is defined as the product of mass of a body and its acceleration.
The S.I unit of Force is Newton (N).
Mathematically Force can be represented as,
F = ma .................. Equation 1
Where F = force, m = mass, a = acceleration.
also
a = (v-u)/t............... Equation 2
Where v = final velocity, u = initial velocity, t = time.
Given: v = 0.60 m/s, u = 0 m/s ( From rest), t= 0.16 s.
Substitute into equation 2
a = (0.60-0)/0.16
a = 3.75 m/s²
Also given: m = 80 g = 0.08 kg.
Substitute into equation 1,
F = 0.08(3.75)
F = 0.3 N.
Hence he average force = 0.3 N
The right option is d. 0.3 N
Space is more hostile to the human body.
Answer:C
Explanation:
Power=280watts=280/1000 kilowatts
Power=0.28 kilowatts
Device use 0.28 kilowatts in 1 day
1day=24hours
Device use 0.28 kilowatts in 24hours
30days=30 x 24=720 hours
For 720 hours=(0.28x720) ➗ 24
For 720 hours=201.6 ➗ 24
For 720 hours=8.4
