A student has an 80 g sample of a radioactive material that has a half-life of 20 seconds. How much material will he have left after 60 seconds? A.
10 g

B.
20 g

C.
40 g

D.
5 g

World class speed skaters can skate a 3,000-m course in about 4 minutes. what is their average speed for this course? a. 12.5 m/sb. 1.33 m/sc. 1.25 m/sd. 13.3 m/s

Using gravity, an elephant can pull a mouse towards it from the ground. true or false explain why. will give brainliest if answered fast and the best explanation

Determine the time it takes for a satellite to orbit the earth in a circular "near-earth" orbit. the definition of "near-earth" orbit is one which is at a height above the surface of the earth which is small compared to the radius of the earth, so that you may take the acceleration due to gravity as essentially the same as that on the surface. does your result depend on the mass of the satellite?