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horsena [70]
3 years ago
13

In which situation is no work being done? A. a person carrying a box from one place to another B. a person picking up a box from

the ground C. a person pushing a box from one place to another D. a person pulling a box from one place to another
Physics
2 answers:
Softa [21]3 years ago
7 0

Answer:

A person carrying a box from one place to another.

Explanation:

The work done is defined as the product of force, displacement and the angle between the force and displacement. Mathematically, it can be written as :

W=F.d

W=Fd\ cos\ \theta

Where

\theta is the angle between the force and the displacement

When \theta=90^0, then W = 0 (since, cos 90 = 0)

The situation in which no work being done is (a) " a person carrying a box from one place to another". In this case, the force acting on the person is gravitational force only which acts in downward direction and the person is carrying box from one place to another. So, the angle between the force and displacement is 90 degrees. Hence, no work being done.

Anastaziya [24]3 years ago
6 0

Picking up a box, pushing a box along the ground, and pulling a box along the ground (B, C, and D) definitely involve work being done.

If a person CARRIES a box from one place to another, AND keeps it at the same height during the entire carry, then no work is done. ( A )

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Answer:

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5 0
3 years ago
In one cycle, a heat engine takes in 1000 J of heat from a high-temperature reservoir, releases 600 J of heat to a lower-tempera
Talja [164]

Answer:

η = 40 %  

Explanation:

Given that

Qa ,Heat addition= 1000  J

Qr,Heat rejection= 600 J

Work done ,W= 400 J

We know that ,efficiency of a engine given as

\eta=\dfrac{W(net)}{Q(heat\ addition)}

Now by putting the values in the above equation ,then we get

\eta=\dfrac{400}{1000}

η = 0.4

The efficiency in percentage is given as

η = 0.4  x 100 %

η = 40 %

Therefore the answer will be 40%.

4 0
3 years ago
Give 1 real life example of a scenario that takes advantage of the inverse relationship between force and time when impulse is c
OverLord2011 [107]

Answer:

On real life example of a scenario that takes advantage of the inverse relationship between force and time when impulse is constant is when making a serve with a lawn tennis racket

How It is an example of impulse is that when a serve is made by moving the bat slowly, the lawn tennis player uses less force and the ball is in contact with the string for longer a period

When however, the lawn tennis player moves the racket faster, with the strings of the racket highly tensioned  he uses more force and the ball also spends less time on the racket to produce the same momentum

Explanation:

The impulse of a force, ΔP is given by the following formula;

ΔP = F × Δt

Where ΔP is constant, we have;

F ∝ 1/Δt

Therefore, for the same impulse, when the force is increased, the time of contact is decreases and vice versa.

7 0
3 years ago
Can you label the parts of the eye?
photoshop1234 [79]

Answer:

  1. Iris
  2. Pupil
  3. Corona
  4. Anterior chamber
  5. lens
  6. Vitreous humor
  7. Blood vessels
  8. Optic nerve
  9. Hyaloid canal
  10. Retina

Hope it helps :)

7 0
3 years ago
A student makes a short electromagnet by winding 300 turns of wire around a wooden cylinder of diameter d 5.0 cm. The coil is co
kupik [55]

Answer:

A) μ = A.m²

B) z = 0.46m

Explanation:

A) Magnetic dipole moment of a coil is given by; μ = NIA

Where;

N is number of turns of coil

I is current in wire

A is area

We are given

N = 300 turns; I = 4A ; d =5cm = 0.05m

Area = πd²/4 = π(0.05)²/4 = 0.001963

So,

μ = 300 x 4 x 0.001963 = 2.36 A.m².

B) The magnetic field at a distance z along the coils perpendicular central axis is parallel to the axis and is given by;

B = (μ_o•μ)/(2π•z³)

Let's make z the subject ;

z = [(μ_o•μ)/(2π•B)] ^(⅓)

Where u_o is vacuum permiability with a value of 4π x 10^(-7) H

Also, B = 5 mT = 5 x 10^(-6) T

Thus,

z = [ (4π x 10^(-7)•2.36)/(2π•5 x 10^(-6))]^(⅓)

Solving this gives; z = 0.46m =

3 0
3 years ago
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