What is the mass of this object?

Question

when a constant force is applied to an object, the acceleration of the object varies inversely with its mass. when a certain constant force acts upon an object with mass 6 kg, the acceleration of the object is 7 m/s^2. when the same force acts upon another object, its acceleration is 3 m/s^2. what is the mass of this object

Answer 1

By Newton's Second Law, the force on an object is F = ma where m is the mass of the object and a is the acceleration. Let's write a force equation for both of these circumstances. First we have F = 6kg(7 m/s^2). We also have F = m(3 m/s^2). We can equate the two equations together since the force acting upon these two masses is the same. So, now we have 6kg(7 m/s^2) = m(3 m/s^2). After dividing by 3 m/s^2 on both sides to isolate m, the mass of the second object, we have (6kg(7 m/s^2))/3 m/s^2 = m. Therefore after some calculations, we have m = 14 kg.

Answer 2

6 kg : 7 m/s² :: x kg : 3 m/s²

7x kg m/s² = 18 kg m/s²

Can you solve for x and answer?