If you double the mass of an object, how much do you need to change the force to achieve the same acceleration

The force must be doubled as well

Explanation:

According to Newton's second law of motion, the force exerted on an object is directly proportional to its mass and acceleration :

(1)

Isolating :

(2)

Now if the mass is doubled it will be now and if we want to keep the same acceleration (2), the force also must be doubled, as follows:

(3)

if you already have the answer to (a), then just work out how many periods there are in 1 minute, and that's the answer to (c).

i don't know that i agree with that but what's the question ?