What is the mass of an object that needs a force of 4,300 N to accelerate it at a rate of 4 m/sec2

Question

What is the mass of an object that needs a force of 4,300 N to accelerate it at a rate of 4 m/sec2

Answer 1

First, let's think about what information was given to us.

We have Force, in Newtons: 4,300N.

We also have acceleration, in m/s²: 4m/s².

And finally we have mass, in kilograms, though we don't know exactly how much mass yet.^*

Our first thought when looking at a question like this should be "what formulas do I know that include these units?" In this case, you've probably seen the equation F=MA in class. That is, Force is equal to Mass times Acceleration.

If we rearrange that equation, it becomes Force divided by Acceleration equals Mass, or

F/A = M.

If we plug in our given numbers, we get M = 4300/4, or M = 1,075.

Again, we know that our mass should be in kg. Note that Newtons, our unit for force, is another way of saying "meters • kilograms • m/s²". See that kilograms in the definition? That's a really good hint that our answer is automagically in kilograms.

So, out final answer is: the mass of such an object must be 1,075kg.

*we can assume Kilograms, because Kilograms are the "base SI unit" for mass. If you have not learned about SI units in class, it's a list of units that Science people consider to be the international standard so no one gets confused.