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3 years ago

A Porter carries a 25 kg suitcase a distance of 1 km. Explain why the Porter does no work

Physics

1 answer:

il63 [147K]3 years ago

8 0

The Porter does no work because the force applied is perpendicular to the displacement

Explanation:

The work done by a force applied to an object is given by:

$W=Fd cos \theta$

where

F is the magnitude of the force

d is the displacement

$\theta$ is the angle between the direction of the force and the displacement of the object

From the formula, we notice that:

- The work done is maximum when the force is parallel to the displacement (because $\theta = 0^{\circ}, cos 0^{\circ}=1$ )

- The work done is zero when the force is perpendicular to the displacement (because $\theta = 90^{\circ}, cos 90^{\circ}=0$ )

In this problem, Porter is carrying the suitcase: this means that the force he is applying is upward (to balance the weight of the suitcase, pulling down), while the displacement is in the horizontal direction: therefore, force and displacement are perpendicular, so the work done is zero.

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The first mechanized industry was

Oxana [17]

C. Textiles

It was the first thing mechanized in the Industrial Revolution

3 0

2 years ago

the focal length of a simple magnifier is 8.50 cmcm . assume the magnifier to be a thin lens placed very close to the eye.

Igoryamba

When the object is at the focal point the angular magnification is 2.94.

Angular magnification:

The ratio of the angle subtended at the eye by the image formed by an optical instrument to that subtended at the eye by the object when not viewed through the instrument.

Here we have to find the angular magnification when the object is at the focal point.

Focal length = 6.00 cm

Formula to calculate angular magnification:

Angular magnification = 25/f

= 25/ 8.5

= 2.94

Therefore the angular magnification of this thin lens is 2.94

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5 0

10 months ago

Explain different types of thermometer and their thermometry substance

Rudiy27

Answer:

Explained below

Explanation:

1) Liquid in glass thermometer: This type of thermometer is used primarily to measure the temperatures from inspection of changes in volume of liquid.

Thermometry substance is mercury or alcohol

2) Gas thermometer: This type is used to measure temperature as a result of changes in gas pressure or volume.

Thermometry substance is Gas.

3) Resistance thermometer: This type is used to measure temperature due to changes in electric resistance.

Thermometry substance is Resistance wire.

4) Thermocouple thermometer: This type is used to measure the temperature due to changes in electrical potential difference occurring between two metal junctions.

Thermometry substance is two wires that are dissimilar.

5) Bimetallic thermometer: This is a type of thermometer that measures temperature by converting temperature into mechanical displacement by making use of Bimetallic strip.

Thermometry substance is two metals that are dissimilar.

3 0

3 years ago

A wave has a wavelength of 7 mm and a frequency of 9 hertz. What is its speed?

Snezhnost [94]

Speed of wave = Frequency x Wavelength
so Speed = 0.7 x 9 = 6.3

remember the calculations must be done in their Basic SI units.
therefore, you have to convert 7 mm to meters which becomes 0.7 meters

8 0

3 years ago

NASA is giving serious consideration to the concept of solar sailing. A solar sailcraft uses a large, low- mass sail and the ene

RUDIKE [14]

Answer:

d. The sail should be reflective because in this case the momentum transferred to the sail per unit area per unit time is larger than for absorbing sail, therefore the radiation pressure is larger for the reflective sail.

Explanation:

Let us take the momentum of a photon unit as u

we know that the rate of change of momentum is proportional to the force exerted.

For a absorbing surface, the photon is absorbed, therefore the final momentum is zero. From this we can say that

F = (u - 0)/t = u/t

for a unit time, the force is proportional to the momentum of the wave due to its energy density. Therefore,

F = u

For a reflecting surface, the momentum of the wave strikes the sail and changes direction. Since we know that the speed of light does not change, then the force is proportional to

F = (u - (-u))/t = 2u/t

just as the we did above, it becomes

F = 2u.

From this we can see that the force for a reflective sail is twice of that for an absorbing sail, and we know that the pressure is proportional to the force for a given area. From these, we conclude that the sail should be reflective because in this case the momentum transferred to the sail per unit area per unit time is larger than for absorbing sail, therefore the radiation pressure is larger for the reflective sail.

3 0

3 years ago