Question

speed of light is 3×10^8m/sec. the circumference equador is 4×10^4km. if light turns around equador for 5 min, how many tours can we count?​

Answer 1

Answer: 2250 tours

Explanation:

We have the following data:

Speed of light: $c=3(10)^{8}m/s$

Circumference of the equador: $r=4(10)^{4}km \frac{1000 m}{1 km}=4(10)^{7}m$

The time in which light turns around equator: $t=5 min \frac{60 s}{1 min}=300 s$

We need to find how many tours does light do around the equator in $t=300 s$

Let's begin by the expression of the speed, which is a relation between the traveled distance ($d$) and time:

$c=\frac{d}{t}$ (1)

Isolating $d$:

$d=c.t$ (2)

$d=(3(10)^{8}m/s)(300 s)$ (3)

$d=9(10)^{10}m$ (4) This is the distance light travels in 5 min.

Now we need to know to how many tours is this distance equivalent, we can know this by a Rule of three:

1 tour ---- $r$ (circumference of the equator)

? tour ---- $d$

Then:

$?=\frac{(1 tour)(d)}{r}$

$?=\frac{(1 tour)(9(10)^{10}m)}{4(10)^{7}m}$

$?=2250 tours$ This is the count of tours in 5 minutes.