To determine the distance of the light that has traveled given the time it takes to travel that distance, we need a relation that would relate time with distance. In any case, it would be the speed of the motion or specifically the speed of light that is travelling which is given as 3x10^8 meters per second. So, we simply multiply the time to the speed. Before doing so, we need to remember that the units should be homogeneous. We do as follows:
distance = 3x10^8 m/s ( 8.3 min ) ( 60 s / 1 min ) = 1.494x10^11 m
Since we are asked for the distance to be in kilometers, we convert
distance = 1.494x10^11 m ( 1 km / 1000 m) = 149400000 km
The work done by the elephant to lift one log is the force multiplied by the height at which the log has been lifted:
And so, the total work done to lift the 7 logs is 7 times the work done to lift each log:
I know it, X-rays<span>, </span>gamma rays<span> and beta particles are all </span>used<span> in medicine to treat internal organs. X-</span>rays<span> are produced by firing electrons at a metal target and </span>gamma rays<span> are emitted by the nucleus of radioactive atoms. </span>Gamma rays<span> are </span>used<span> to kill cancer cells, to sterilise medical equipment and in radioactive tracers.</span>
21. light changes its direction when travelling through a new medium because denser mediums have a higher angle of refraction.
The answer is going to be B
