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katen-ka-za [31]

3 years ago

6

A motorist travels first part of a trip at an average speed of 35 km/h and covers an equal distance in the second part. If he ha

s completed his trip at an average speed of 21 km/h then his average speed in the second half is ------- km/h

1 answer:

Jlenok [28]3 years ago

7 0

The average speed of the motorist in the second half of the journey is determined as 7 km/h.

<h3>What is average speed?</h3>

The average speed of an object is the ratio of total distance to total time of motion.

Let his average speed in the second half = x

21 = (35 + x) / 2

35 + x = 42

x = 42 - 35

x = 7 km/h

Thus, the average speed of the motorist in the second half of the journey is determined as 7 km/h.

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calculate the diameter of a silver wire of length 75cm , which is extended by 1.85mm when a 10kg mass is suspended from it's end

sdas [7]

Answer: $0.8\ mm$

Explanation:

Given

length of wire $l=75\ cm$

change in length $\Delta l=1.85\ mm$

mass of wire $m=10\ kg$

Young's modulus for silver $E=7.9\times 10^{10}\ N/m^2$

load on wire $F=mg$

$F=10\times 9.8=98\ kg$

change in length is given by

$\Delta l=\dfrac{Pl}{AE}$

Where A=area of cross-section

$A=\dfrac{Pl}{\Delta lE}$

$A=\dfrac{98\times 0.75}{1.85\times 10^{-3}\times 7.9\times 10^{10}}$

$A=\dfrac{73.5}{14.615\times 10^{7}}$

$A=5.029\times 10^{-7}\ m^2$

also wire is the shape of cylinder so cross-section is given by

$A=\dfrac{\pi d^2}{4}=5.029\times 10^{-7}\ m^2$

$\Rightarrow d^2=\dfrac{5.029\times 10^{-7}\times 4}{\pi }$

$\Rightarrow d^2=64.02\times 10^{-8}$

$\Rightarrow d=8\times 10^{-4}\ m$

$\Rightarrow d=0.8\ mm$

4 0

3 years ago

Consider the following statements. A. Heat flows from an object at higher temperature to an object at lower temperature; B. Heat

IgorC [24]

Only ' A ' is always true.<em> (choice-1)</em>

' B ' is not true when you drop a red hot spoon into cold soup.

' C ' is not true when you drop a red hot marble into a cool swimming pool.

8 0

3 years ago

Which of the following scenarios would most likely be considered pseudoscience?

natali 33 [55]

The belief that the stars determine our fate is considered to be pseudoscience .

Large celestial bodies called stars are mostly made of hydrogen and helium, and in their cores, churning nuclear forges produce light and heat. Except for our sun, all of the other stars in the sky that we can see are light-years from the our planet i.e. earth.
Celestial bodies, also referred to as heavenly bodies, are celestial objects in space, including the sun, moon, planets, and stars. They are a component of the vast universe that we exist in and are normally fairly far away from us.

Pseudoscience, which is defined as an activity that purports to be scientific but is actually not, is defined as seems science. Science does not engage in extraterrestrial affairs it simply studies the natural world. Science cannot provide an answer to morality, immorality, or questions of meaning or purpose, but it does require ethical behavior. In other hand astronomy is regarded as pseudoscience since no link between the locations of the stars and human behavior can be demonstrated using evidence from science.

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3 0

1 year ago

Read 2 more answers

What are some of the differences between solids, liquids, and gases?

9966 [12]

Answer:

SOLIDS LIQUIDS

Have a definite shape. Don't have a definite shape.

Have a definite mass. Have a definite mass.

Have a definite volume. Have a definite volume.

GASES

Have a definite mass.

Don't have a definite volume.

Don't have a definite shape.

DEFINITE- CLEARLY STATED OR EXACT TRUTH ABOUT A FACT.

Explanation:

7 0

3 years ago

A current 1A in the human body is extremely dangerous.

zmey [24]

a) Potential difference needed: 10,000 V

b) Because the potential difference in the house is maximum 230 V

Explanation:

a)

The relationship between current, potential difference and resistance in a conductor is given by Ohm's law:

$V=RI$

where

V is the potential difference

R is the resistance

I is the current

The resistance of the human body is estimated to be as high as $100,000 \Omega$ for a dry body and as low as $1000 \Omega$ for a wet body: in this problem, we use a value in the middle,

$R=10,000 \Omega$

Therefore, the potential difference needed to produce a current of

$I=1 A$

is

$V=(10,000)(1)=10,000 V$

b)

Here we want to estimate if it is likely or not to get injured by an electric current in a house.

The amount of current that can be fatal is $I=1 A$ . From part a), we saw that in order to produce this current through the human body, a potential difference of

$V=10,000 V$

is needed.

However, the electricity that reaches the houses and then is connected to the household appliances has a potential difference of

V = 230 V

This value is much lower than 10,000 V, therefore the electricity in the house is unlikely to cause injures to human body.

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6 0

3 years ago