The graph below shows the decay of a radioactive isotope. what is the half-life of the isotope?
a. 15 seconds
b. 25 seconds
c. 40 seconds
d. 200 seconds
the graph is in an attachment. : )

An electric current is flowing through the cord below.what will happen to this current if a magnet is brought near the cord? a. the electric current will stop flowing. b. it will exert a force on the voltage. c. the resistance of the wire will decrease. d. it will exert a force on the electric current.

Which is not an example of how an object gains elastic potential energy by stretching? a. jumping on a pogo stick b. pulling on a rubber band c. jumping on a trampoline

Asynthetic fiber used in manufacturing carpet has tensile strength that is normally distributed with mean 75.5 psi and standard deviation 3.5 psi. how is the standard deviation of the sample mean changed when the sample size is increased from n equals 8 to n equals 47