The first experiment that was made to attempt to measure the speed of light involved detonating gunpowder by Isaac Beeckman. He declared that his experiment was inconclusive. Galileo also tried to measure the speed of light using two lanterns placed across each other. The next experiment involved planets where Ole Romer based his calculation on its movements. The final calculations were derived from different theories by different scientists including Maxwell until it ended up with the exact value for the speed of light.
Answer:
-200 N
Explanation:
The cabinet moves at constant velocity, so that means there's no acceleration.
Applying Newton's second law to the cabinet:
∑F = ma
F + 200 = 0
F = -200
The friction force is 200 N in the opposite direction.
Answer:
72,300 years.
Explanation:
- Initial mass of this sample: 504 grams;
- Current mass of this sample: 63 grams.
What's the ratio between the current and the initial mass of this sample? In other words, what fraction of the initial sample hasn't yet decayed?
.
The value of this fraction starts at 1 decreases to 1/2 of its initial value after every half-life. How many times shall 1/2 be multiplied to 1 before reaching 1/8? 
. It takes three half-lives or 
years to reach that value.
In certain questions the denominator of the fraction is large. It might not even be an integer power of 2. The base-x logarithm function on calculators could help. Evaluate
to find the number of half-lives required. In case the base-x logarithm function isn't available, but the natural logarithm function 
is, apply the following expression (derived from the base-changing formula) to get the same result:
.
