Determine the activity of the sample of cerium when the sample was 80 seconds old

Select all of the following that are equal to an impulse of 20 unitsa) force= 5, time= 5.5b) force= 25, time= 0.8c) force= 0.1, time= 200d) force= 10, time= 2(its b, c, and d)(also in order to find answer they have to add to get the unit)ex= 25x.8=20 or .1x200=20

How many neutrons does element x if it’s atomic number is 28 and its mass number is 87

Why does gravity have a lesser than grater effect on higher altitudes?