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inna [77]
3 years ago
9

A man has been guarding a house for one hour . Why is it not considered work in science

Physics
1 answer:
leva [86]3 years ago
8 0

Answer: because there is no displacement or movement in the watchman's work. according to science when displacement or movement take place it is said to be work. hope this helps you.

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A ball of 10kg falls from rest from a height of 150m, Neglating air resistance, calculate its kinetic energy after falling a dis
GaryK [48]

Answer: 3920\ J

Explanation:

Given

mass of ball m=10 kg

It is placed at a height of 150 m

It is dropped from the height and allowed to free fall for 40 m

Velocity acquired by the ball during this fall is given by v^2-u^2=2as

Insert u=0, a=g

\Rightarrow v^2-0=2\times 9.8\times 40\\\Rightarrow v=\sqrt{784}\\\Rightarrow v=28\ m/s

Kinetic energy at this instant

K.E.=\dfrac{1}{2}\times 10\times 28^2\\\\\Rightarrow K.E.=3920\ J

3 0
3 years ago
A piece of bismuth with a mass of 4.06 g 4.06 g gains 423 J 423 J of heat. If the specific heat of bismuth is 0.123 J / ( g ° C
Sholpan [36]

Answer: 846°C

Explanation:

The quantity of Heat Energy (Q) required to heat bismuth depends on its Mass (M), specific heat capacity (C) and change in temperature (Φ)

Thus, Q = MCΦ

Given that:

Q = 423 joules

Mass of bismuth = 4.06g

C = 0.123 J/(g°C)

Φ = ?

Then, Q = MCΦ

423 J = 4.06g x 0.123 J/(g°C) x Φ

423 J = 0.5J/°C x Φ

Φ = (423J/ 0.5g°C)

Φ = 846°C

Thus, the change in temperature of the sample is 846°C

4 0
4 years ago
A step index fiber has a numerical aperture of NA = 0.1. The refractive index of its cladding is 1.465. What is the largest core
Vladimir [108]

Answer:

diameter = 9.951 × 10^{-6} m

Explanation:

given data

NA = 0.1

refractive index = 1.465

wavelength = 1.3 μm

to find out

What is the largest core diameter for which the fiber remains single-mode

solution

we know that for single mode v number is

V ≤ 2.405

and v = \frac{2*\pi *r}{ wavelength} NA

here r is radius    

so we can say

\frac{2*\pi *r}{ wavelength} NA    = 2.405

put here value

\frac{2*\pi *r}{1.3*10^{-6}} 0.1    = 2.405

solve it we get r

r = 4.975979 × x^{-6} m

so diameter is = 2  ×  4.975979 × 10^{-6} m

diameter = 9.951 × 10^{-6} m

3 0
3 years ago
2. A truck is traveling east through mud that is slowing down its speed. With west defined as negative, which of the following i
Lynna [10]

Hi! The answer is C

As west is defined as negative, the trucks velocity is positive, since its travelling east. But its speed (absolute value of velocity) is decreasing, that means that the acceleration is negative.  

3 0
3 years ago
In a lesson about the behavior of gases, Genaris and her classmates learn that the volume of a gas is affected by its temperatur
Liula [17]
<span>To know if there were other factors that affected the volume of a gas, Genaris and her classmates should: </span>"formulate a new hypothesis with the same dependent variable but a different independent variable as the original hypothesis." In this case, the dependent variable is the volume of the gas and the new independent variable is a factor they think will affect the volume of the gas.
7 0
4 years ago
Read 2 more answers
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