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azamat
3 years ago
15

A rock falls from a vertical cliff that is 4.0 m tall and experiences no significant air resistance as it falls. At what speed w

ill it's gravitational potential energy (relative to the base of the cliff) be equal to its kinetic energy in m/s?
Physics
1 answer:
Zinaida [17]3 years ago
8 0

Answer:

v = 6.3 m/s

Explanation:

  • Since no significant air resistance exists, total mechanical energy must be kept constant at any time.
  • At the top of the cliff, all the energy is gravitational potential energy, as follows:

       E_{i}  = K_{i} + U_{i} = 0 + U_{i}  (1)

  • If we choose the ground level as our zero reference level for the gravitational potential energy, Ui is simply:
  • Ui = m*g*h (1)
  • At any height, the sum of the kinetic and the gravitational potential energy must be equal to (1).
  • We know from the question, that at the point of interest, both types of energies must be equal each other, so we can write the following expression from (1):

       m*g* h = 2*\frac{1}{2}*m*v^{2}  (2)

  • Dividing both sides by m, simplifying, and solving for v, we get:

       v = \sqrt{g*h} =\sqrt{9.8m/s2*4.0m} = 6.26 m/s (3)

  • v = 6.3 m/s (with two significative figures)
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Answer:

(a) 1.939 m/h

(b) 0.926 m/h

(c) -0.315 m/h

(d) -1.21 m/h

Explanation:

Here, we have the water depth given by the function of time;

D(t) = 7 + 5·cos[0.503(t-6.75)]

Therefore, to find the velocity of the depth displacement with time, we differentiate the given expression with respect to time as follows;

D'(t) = \frac{d(7 + 5\cdot cos[0.503(t-6.75)])}{dt}

= 5×(-sin(0.503(t-6.75))×0.503

= -2.515×(-sin(0.503(t-6.75))

= -2.515×(-sin(0.503×t-3.395))

Therefore we have;

(a) at 5:00 AM = 5 -  0:00 = 5

D'(5) =  -2.515×(-sin(0.503×5-3.395)) = 1.939 m/h

(b) at 6:00 AM = 6 -  0:00 = 6

D'(5) =  -2.515×(-sin(0.503×6-3.395)) = 0.926 m/h

(c) at 7:00 AM = 7 -  0:00 = 7

D'(5) =  -2.515×(-sin(0.503×7-3.395)) = -0.315 m/h

(d) at Noon 12:00 PM = 12 -  0:00 = 12

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3 years ago
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Explanation:

Acceleration due to gravity is as a result of the gravitational force of attraction of a planet to its centre.

g = GM/r^2

Where;

g = acceleration due to gravity

G = gravitational constant

M = mass of planet

r = radius of planet

Given that the two planet have the same radius, if the mass of planet a is twice the mass of planet b the the acceleration due to gravity of planet a would be twice that of planet b, because acceleration due to gravity is directly proportional to the mass of the planet.

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how much water is needed to produce 1kwh of electricity at a power plant that is 30% efficient if the temperature increase 10 C
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Explanation:

The amount of energy that we need to produce with the power plant is

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The amount of water that is needed to produce this energy can be found using the equation

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And solving for m, we find:

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Learn more about specific heat capacity:

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