Simple Physics Questions...?

Question

There are two questions. I just learnt physics and i'm a little messed up. So i really need help. Just give me the workings and explanations and 10 points to you!

Speed of light: 300 000 000m/s

Speed of Sound in Air: 343m/s

Question: If the time difference between hearing a thunder and seeing a lightning is 1 s, approximately how far is the thunderstorm away from you?

Here's the second question:

Speed of human sprinter: 10m/s

Question: Express the speed of the human sprinter in km/h.

Thanks!

Answer 1

Let the distance of the thunderstorm be x meter.

Time taken by sound = x/343 s

Time taken by light = x/300 000 000 s

Difference = x/343 - x/x/300 000 000 s

It is given that time difference is 1s

Therefore, x/343 - x/x/300 000 000 = 1

Or, x(1/343 - 1/300 000 000) = 1

1/300 000 000 is negligible compared to 1/343.

So, x/343 = 1

Or, x = 343

Ans: 343 m

Second question:

1 m = 1/1000 km

1 s = 1/3600 h

10m/s = 10*(1/1000)/(1/3600) km/h

=10*3600/1000 km/h = 36 km/h

Answer 2

A gap of 4 seconds between seeing the lightning flash and hearing the thunder means that the bolt grounded about 1 mile away from your position.

Edit; Your runner is clocking 36 kmh/ 22.6 mph

Thank you ♫♥Jingyu♥♫

Answer 3

aprox 343 meter and the sprinter goes  .01km/s

Answer 4

a)  343 meters (if you wish to forget about error in measurement, 342.9999988559 meters) from you is where the lightning struck.  The thunderstorm can be anywhere.

b)  36 km/hr

You haven't learnt physics.  Or learned either.  You're just starting.

Be sure to show your work.

... and Marty, the gap is 4.7 seconds, not 4.  You're guesstimate is 17% off.

Answer 5

The speed of light is so fast that you can forget about it. Assume that you see the lightning at the same time that it happens. So if it takes the sound 1 second to get to you, and it travels at 343 metres per second, it must have started 343 metres away.

To convert metres per second to metres per hour, multiply by 3600, the number of seconds in an hour.

Then you can convert metres per hour into kilometres per hour by dividing by the number of metres in a kilometre, which is 1000.

Answer 6

the first question, as in a great deal of physics questions, can be solved with simultaneous equation (a set of equations with at least one common unknown) btw 300000000 = 3 x 10^8 in case you didnt know

for light:

speed = distance/time

distance = speed x time

d = 3 x 10^8 x t

for sound:

speed = distance/time

distance = speed x time

d = 343 x (t + 1) <-- because it arrived 1 sec later than lightning (t)

because 'd', the distance of you from the event is the same for lightning and thunder, they are equal. therefore we can say that:

343 x (t + 1) =  3 x 10^8 x t

343t +343 = 3 x 10^8 x t

343 = (3 x 10^8)t -343t

343 = 299999657t

t = 343/299999657

  = 1.14 x 10^-6 seconds

this is time the lightning took to reach you.

therefore

speed = distance/time

distance = speed x time

d = 3 x 10^8 x 1.14 x 10^-6

   = 342 metres

thus the answer is 342 metres away from you.

i could have taken a more direct route to the answer, but i got there eventually.

question 2:

10m/s x 1km/1000m x 3600 sec/hour = 36 km/h

Answer 7

Q2=36 km\h sorry I cannot show you the workings as I've for gotten the correct formular,however this is simple enough to do in my head.

Sorry I can't realy help you much as I've left my study guide @ home,but best of luckConverting km/h to m/s

Answer 8

well i guess it would be 343 meters from you, multiply that by 39 for inches in a meter (roughly), then divide by 12 for feet. 1114 ft, 9 inches distance.  the speed of the light does not matter since at this distance it is essentially instantaniously.

secondly 10 meters per second, would be 600 meters per minute, then 36,000 meters per hour divide by 1000 for km, so 36 km/hour.  hope this helps.