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reema

@reemz.malik

Rocker

+ 3

Posted: 14 years ago

#61

@Komal - Thanx a lot. That really helped I might use similar example :D

Am so glad IF opened up Homework help...or else math would have made me crazy 😆

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596277

Suspended

Posted: 14 years ago

#62

Physics Question - - - - Period and Frequency

What is the period of the minute hand of a clock?

Formula for Period is time/cycle

The formula is confusing me now, cause I believe the answer is 3600s, but I only get that by multiplying 60 by 60, and if I do it that way, then Im not following the formula, so how exactly do I do this?

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akhl

@akhl

Dazzler

Posted: 14 years ago

#63

@Ayeshaa,
The minute hand completes one revolution in 1 hour i.e. 3600 s
This means if cycle = 1, then time = 3600 s
Period = 3600 s/1 = 3600 s

You can also say that period is the time taken to complete one cycle.

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596277

Suspended

Posted: 14 years ago

#64

^^ Thanks so much buddy =)

I have one last question on this Physics worksheet, and I even asked the sub about it, and she was confused.

The crankshaft of a car engine is turning at 3.6*10^2 r/min. Four of its eight spark plugs fire during each revolution, at equal time intervals. The coil provides that spark for all the plugs.

A) How many sparks does the coil produce per second?

b) What is the time between sparks?

I just don't get how to do this, the "four out of eight" thing confuses me:\

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akhl

@akhl

Dazzler

Posted: 14 years ago

#65

@Ayeshaa, in 4 our of 8, only 4 is important because 4 sparks fire in one revolution.

a) (3.6 * 10^2 r/min) * (4 sparks/r)
= 3.6 * 10^2 * 4 sparks/min
= 3.6 * 10^2 * 4/60 sparks/second
= 24 sparks/second

Ans: 24

b) For sparks, frequency = 24 s^-1
Time between spakrs = period = 1/frequency = (1/24) second
If you want to write in decimal, then the answer is
4.2 * 10^-2 second

Edited by akhl - 14 years ago

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596277

Suspended

Posted: 14 years ago

#66

^^ Thanks:) I'll go over what you did, and If I still don't understand it, then I'll ask you.

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596277

Suspended

Posted: 14 years ago

#67

Originally posted by: akhl
@Ayeshaa, in 4 our of 8, only 4 is important because 4 sparks fire in one revolution.

a) (3.6 * 10^2 r/min) * (4 sparks/r)
= 3.6 * 10^2 * 4 sparks/min
= 3.6 * 10^2 * 4/60 sparks/second
= 24 sparks/second

Ans: 24

b) For sparks, frequency = 24 s^-1
Time between spakrs = period = 1/frequency = (1/24) second
If you want to write in decimal, then the answer is
4.2 * 10^-2 second

Okay just want to ask that you did you use a specific formula for part a? And also where did you get the -1 from in part b?

--Sorry I just don't really get this stuff:\

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Harjot.

@Angel-Jot

Alumni

+ 6

Posted: 14 years ago

#68

Guys. The first page, third reserved post has been edited. In it i've posted everyone who has said that they can help with a certain subject. So check that if you want. Also links provided here are also posted there.

And, i can help with English, French and Canadian History if you need help. 😃

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akhl

@akhl

Dazzler

Posted: 14 years ago

#69

@Ayeshaa,
For part a, we have to find how many sparks fire in one second.
This means we need sparks/second
Formula is not needed.
Question gives 3.6 * 10^2 r/min and 4 sparks/r
If you multiply them, then r and r will cancel and you are left with sparks/min
You know 1 min = 60 s, therefore you can convert it into sparks/second

In part b, the unit is sparks/second. The second is in denominator, which can be written as second^-1 which I shortened to s^-1. We can skip "sparks" because we already know that we are talking about sparks.

Edited by akhl - 14 years ago

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akhl

@akhl

Dazzler

Posted: 14 years ago

#70

@Ayeshaa,
Another way to understand part a is
3.6 * 10^2 revolutions in 1 min
Or, 3.6 * 10^2 revolutions in 60 s
Therefore, 1 revolution in 60/(3.6*10^2) s i.e. 1/6 s
Also, 4 sparks fire in 1 revolution

Therefore, in 1/6 s, 4 sparks fire
In 1 s, 4 * 6 = 24 sparks fire

Another way to understand part b is
24 sparks fire in one second.
This means after a spark has fired, 24 more sparks will fire in 1 second.
Therefore, after a spark has fired, 1 more spark will fire in 1/24 second
Therefore, time between two sparks = 1/24 second

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