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timama [110]
2 years ago
13

The burj Khalifa in Dubai is the worlds tallest building. It rises to an amazing 828M above the ground and if you were to get to

the top using the stairs, you would climb a total of 3234 steps!
If each of these steps has a depth of 20CM, calculate the total work done by a man of weight 800N who climbs to the top of the stairs?
Physics
1 answer:
antoniya [11.8K]2 years ago
6 0
I don't understand what you mean by "depth" of the steps.  The flat part of the step has a front-to-back dimension, and the 'riser' has a height.  I don't care about the horizontal dimension of the step because it doesn't add anything to the climber's potential energy.  And if the riser of each step is 20cm high, then 3,234 of them only take him (3,234 x 0.2) = 646.8 meters up off the ground.  So something is definitely fishy about the steps.

Fortunately, we don't need to worry at all about the steps in order to derive a first approximation to the answer ... one that's certainly good enough for high school Physics.

In order to lift his bulk 828 meters from the street to the top of the Burj, the climber has to provide a force of 800 newtons, and maintain it through a distance of 828 meters.  The work [s]he does is (force) x (distance) = <em>662,400 joules. </em>
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Explanation:

According to Faraday's Law, the magnitude of the induced emf in the coil is equal to the rate of changeof the flux linkage through the coil:

\epsilon = \frac{N\Delta \Phi}{\Delta t} (1)

where

N = 505 is the number of turns in the coil

\Delta \Phi is the change in magnetic flux through the coil

\Delta t = 2.77 ms = 2.77\cdot 10^{-3} s is the time interval

\epsilon = 0.166 V

The coil is rotated from a position perpendicular to the Earth's magnetic field to a position parallel to it, so the final flux is zero, and the magnitude of the flux change is simply equal to the initial flux:

\Delta \Phi = B A cos \theta

where

B is the strength of the magnetic field

A is the area of the coil

\theta=0^{\circ} is the angle between the normal to the coil and the field

The area of the coil can be written as

A=\pi r^2

where

r=\frac{15.5 cm}{2}=7.75 cm = 7.75\cdot 10^{-2} m is its radius

Substituting everything into eq.(1) and solving for B, we find:

\epsilon= \frac{NB\pi r^2 cos \theta}{\Delta t}\\B=\frac{\epsilon \Delta t}{\pi r^2 cos \theta}=\frac{(0.166)(2.77\cdot 10^{-3})}{(505)\pi (7.75\cdot 10^{-2})^2(cos 0^{\circ})}=4.8\cdot 10^{-5} T

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8 0
1 year ago
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A disk is spinning about its center with a constant angular speed at first. Let the turntable spin faster and faster, with const
hoa [83]

Answer:

4 (please see the attached file)

Explanation:

While the angular speed (counterclockwise) remained constant, the angular acceleration was just zero.

So, the only force acting on the bug (parallel to the surface) was the centripetal force, producing a centripetal acceleration directed towards the center of the disk.

When the turntable started to spin faster and faster, this caused a change in the angular speed, represented by the appearance of an angular acceleration α.

This acceleration is related with the tangential acceleration, by this expression:

at = α*r

This acceleration, tangent to the disk (aiming in the same direction of the movement, which is counterclockwise, as showed in the pictures) adds vectorially with the centripetal force, giving a resultant like the one showed in the sketch Nº 4.

7 0
1 year ago
To hoist himself into a tree, a 72.0-kg man ties one end of a nylon rope around his waist and throws the other end over a branch
sergij07 [2.7K]

Answer:

man upward acceleration is 0.14m/s^2

Explanation:

given data:

mass of man = 72 kg

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The mass of man of weight 72 kg is hang from two sections of rope, one section pf rope ties around man waist and other section is ties in man hands. when he pulls down the rope  with 360 N force then each section of  rope pulls with 360 N

we know that

Weight= mass × gravity= 72kg × 9.8 = 705.6N

Force = mass× acceleration

Force= -705.6 + (2 × 358) = 10.4 N

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4 0
1 year ago
8. The resistance of a bagel toaster is 14 Ω. To prepare a bagel, the toaster is operated for one minute from a 120-V outlet. Ho
IgorC [24]

Answer: The energy delivered to the toaster is 264.490KJ

Explanation:

Here is the complete question:

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Step-by-step explanation:

Please see attachment below

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A tennis player serves a tennis ball such that it is moving horizontally when it leaves the racquet. When the ball travels a hor
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Answer:

u_x=38.13\ m/s

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We know that g is the constant acceleration in the vertical direction so we can apply the equation of motion in the vertical direction.

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Here u_y=0

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x=u_xt

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t= 0.34 s

So

13=u_x\times 0.34

u_x=38.13\ m/s

So the initial speed of ball is 38.13 m/s.

7 0
1 year ago
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