# physics

posted by
**Vicki**
.

Use the fact that the speed of light in a vacuum is about 3.00x1000 m/s to determine how many kilometers a pulse from a laser beam travels in exactly 1 h

How many seconds are there in 1 hour if there are 60min/hr and 60sec/min?

Then 1hr = 60min/hr x 60sec/min = ?

Then use d=r*t where r is the speed of light and t is the time in seconds you calculated above.

You also need to observe how many meters there are in 1 kilometer:

1km=1000m

i think it is 120 second

well, lets check that...nope

120sec is still only 2 minutes.

The question was asking for a distance, not a time. We multiply the 60min/hr x 60sec/min to get 3,600 sec/hr.

I might also mention that in the original question we need to be aware of how many significant digits the answer should be given with. I think there were only 2 decimal places given for the velocity of light.

i guess i am not sure ok what grade are you going to

Anastasia, well my children are nearly college age so I suppose grade levels don't matter anymore :)