I really need help with 15 and 16 please

  15. 50 kg

  16a. 5 kg

  16b. 3.75 kg

Step-by-step explanation:

The formula relating force, mass, and acceleration can be solved for mass. This formula will apply to both problems. We'll use m for both "mass" and "meters". We presume you can avoid getting mixed up by understanding that meters is used in the context of acceleration: m/s².

  F = ma

  m = F/a . . . . . divide by a

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15. m = (250 N)/(5 m/s²) = 50 kg

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16a. m = (15 N)/(3 m/s²) = 5 kg

16b. m = (15 N)/(4 m/s²) = 3.75 kg

Comment on units

Especially for physics problems, I like to keep the units with the numbers. It is helpful to remember that Newtons are equivalent to kg·m/s². So, dividing Newtons by acceleration in m/s² will give mass in kg. Since you're familiar with F=ma, it's not too hard to remember that the units of force (N) are the product of the units of mass (kg) and acceleration (m/s²).