A researcher measures 200 counts per minute coming from a radioactive source at noon. At 3:00pm, she finds that this has dropped to 25 counts per minute. What percentage of the original source will remain at 6:00pm?

A) 3.125%
B) 4.5%
C) 5.8%
D) 6.25%

1400 kg car has a speed of 27 m/s. if it takes 7 s to stop the car, what is the impulse and the average force acting on the car?

=force × distance a. work b. velocity c. pressure d. momentum

I'm thinking it's 2 you are asked to explain the earth's magnetic field. which is the best reply? 1. the earth's magnetic south is similar to the north pole of a magnet. 2. the earth's core has a strong magnetic charge similar to the south pole of a magnet. 3. the earth's geomagnetic south is similar to the south pole of a magnet. 4. the earth's magnetic charge is not centered at either pole; it varies based on location.