Physics, 21.10.2020 16:01 gmoney58

A 6 gram coin is which is initially at rest is dropped from the observation deck of a skyscraper 300 meters above the street below. Required:
a. What is the work done by gravity on the coin as it falls?
b. Because there is air resistance the coin was slowed and hit the ground with a final velocity of 60 m/s. What is the kinetic energy of the coin at this speed? Joules
c. How much work was lost to air resistance as the coin fell? Joules
d. What is the average force exerted on the coin due to the air resistance as it fell?

Answers: 1

Show answers

Answers

Answer from: emilyf05

a) The work done by gravity on the coin as it falls is 17.653 joules.

b) The kinetic energy of the coin at a speed of 60 meters per second is 10.8 joules.

c) The work lost due to air resistance is 6.853 joules.

d) The average force exerted on the coin due to air resistance as it fell is 0.023 newtons.

Explanation:

a) We must remind that situation with Earth-coin system must be represented by Principle of Energy Conservation and Work Energy Theorem. According to this latter, work done by gravity equals to the change in gravitational potential energy:

$\Delta U_{g} = m\cdot g \cdot \Delta z$ (Eq. 1)

Where:

$\Delta U_{g}$ - Change in gravitational potential energy, measured in joules.

- Mass, measured in kilograms.

- Gravitational accelerations, measured in meters per square second.

$\Delta z$ - Height of the skyscraper, measured in meters.

If we know that $m = 0.006\,kg$ , $g = 9.807\,\frac{m}{s^{2}}$ and $\Delta z = 300\,m$ , the work done gravity on the coin is:

$\Delta U_{g} = (0.006\,kg)\cdot \left(9.807\,\frac{m}{s^{2}} \right)\cdot (300\,m)$

$\Delta U_{g} = 17.653\,J$

The work done by gravity on the coin as it falls is 17.653 joules.

b) By definition of translation kinetic energy, we get the following model:

$K = \frac{1}{2}\cdot m\cdot v^{2}$

Where:

- Kinetic energy of the coin right before hitting the street, measured in joules.

- Speed of the coin, measured in meters per second.

If we get that $m = 0.006\,kg$ and $v = 60\,\frac{m}{s}$ , the kinetic energy at this speed is:

$K = \frac{1}{2}\cdot (0.006\,kg)\cdot \left(60\,\frac{m}{s} \right)^{2}$

$K = 10.8\,J$

The kinetic energy of the coin at a speed of 60 meters per second is 10.8 joules.

c) The work lost due to air resistance is obtained derived from Principle of Energy Conservation and Work-Energy Theorem:

$W_{lost} = \Delta U_{g}-K$ (Eq. 2)

Where $W_{lost}$ is the work lost due to air resistance, measured in joules.

If we know that $\Delta U_{g} = 17.653\,J$ and $K = 10.8\,J$ , the work lost due to air resistance is:

$W_{lost} = 17.653\,J-10.8\,J$

$W_{lost} = 6.853\,J$

The work lost due to air resistance is 6.853 joules.

d) The average force exerted on the coin due to air resistance can be determined by applying definition of work, as air resistance force was antiparallel to the displacement of the coin. That is:

$W_{lost} = F\cdot \Delta z$

$F = \frac{W_{lost}}{\Delta z}$ (Eq. 3)

Where is the average force exerted on the coin due to air resistance, measured in newtons.

If we know that $W_{lost} = 6.853\,J$ and $\Delta z = 300\,m$ , then the average force exerted on the coin is:

$F = \frac{6.853\,J}{300\,m}$

$F = 0.023\,N$

The average force exerted on the coin due to air resistance as it fell is 0.023 newtons.

Answer from: Quest

not moving. pos accel,

The position-time graph describes the motion of a moving object. describe the motion represented by

Answer from: Quest

If there was no gravity then their would be no downword force on the football to have it return the the grownd, and if there was no friction (mainly air friction) then there would be no opposing force the stop the ball from moving through the air allowing the ball to travle ∞.

Another question on Physics

Physics, 22.06.2019 10:30

Arunner is training for an upcoming marathon by running around a 100-m-diameter circular track at constant speed. let a coordinate system have its origin at the center of the circle with the x-axis pointing east and the y-axis north. the runner starts at (x, y) = (50 m, 0 m) and runs 2.5 times around the track in a clockwise direction.

Answers: 1

Answer

Physics, 22.06.2019 15:00

What is the major limitation to the light microscope?

Answers: 1

Answer

Physics, 22.06.2019 19:00

The law of reflection states that the angle of reflection is equal to the angle of

Answers: 1

Answer

Physics, 22.06.2019 22:30

Find v1, the speed of the fluid in the left end of the main pipe. express your answer in terms of h1, h2, g, and either a1 and a2 or γ, which is equal to a1a2.

Answers: 2

Answer

You know the right answer?

A 6 gram coin is which is initially at rest is dropped from the observation deck of a skyscraper 300...

Questions