I'm struggling with the physics here a bit since I'm a complete novice at this. I'm making a character whose main ability is to subvert/play around with the 2nd Law of motion.

Somehow I understand that by doing that he might be able to translate that into superspeed.

My question is, if an individual had the ability to "edit" all the variables/Factors that affect his body(Mass, Force, Acceleration) of the 2nd Law of motion, how would they do this to attain superspeed?

  • $\begingroup$ Unless they can also adapt how quickly they think: Very poorly. $\endgroup$
    – Joe Bloggs
    Commented May 1, 2019 at 10:54
  • $\begingroup$ The `reality-check' tag does not seem appropriate, as you're essentially asking what would happen if they were not subject to reality. $\endgroup$ Commented May 1, 2019 at 13:49
  • 1
    $\begingroup$ @StephenG sure. I took it off $\endgroup$
    – Nass King
    Commented May 1, 2019 at 14:30

3 Answers 3


Newton second law states

the rate of change of momentum of a body is directly proportional to the force applied, and this change in momentum takes place in the direction of the applied force

which in formula goes $F=m \cdot$$ dv \over dt$

The first thing that comes to my mind is that your character can manipulate his/her inertial mass, so that with the same exerted force a greater acceleration can be achieved. This is the same reason why race cars try to be as light as possible, so that they can get greater acceleration.

Let's put down some numbers for your reference. Let's say the character has a mass of 100 kg and can exert a force of 100 N. This means that he/she will be able to accelerate at 1 $m/s^{-2}$, meaning that after 1 second, starting from rest, he/she will be moving at 1 $m/s$.

If he/she can reduce the inertial mass to 10 kg, for the same force he/she will be accelerating at 10 $m/s^{2}$, thus after 1 second he/she will be moving at 10 $m/s$.

Ideally, bringing the inertial mass close to 0 the achievable acceleration would skyrocket to very high values.


It would depend on what you mean by editing all the factors.

Newtons laws state 1) an object will remain at equilibrium unless acted upon by an eternal, unbalanced force. 2) the object will accelerate in the direction of that force. the acceleration is directly proportional to the magnitude of the force, and inversely so to the mass of the object. 3) for every action, there will be an equal and opposite reaction.

Lets look at law 2 then. When a force is applied, an object will accelerate, in the direction of the force. As the amount of force is increased, the acceleration will increase as well. (ie. the speed gained will become more.) You can think of it as pushing a pencil along a desk, compared to smacking it across the desk. As the mass of the object becomes greater, the acceleration will become smaller. You can think of it again with the pencil, but then go outside and try to push your car.

Now we have that out of the way, we can look at how to edit the law.

Changing mass

If you reduce the mass, a smaller amount of force is needed to achieve the same acceleration, or, the same amount of force would result in a much greater acceleration. If once you have achieved a good speed, you again increase the mass, and with some hand waving preserve the speed, you will have enough momentum to keep the object moving fast for a long time.

Changing force

Theres no plausible way i can picture where you can change the force that something creates, However you might be able to do something of modifying the parts about the directly proportional acceleration, into something exponential, which would lead to

Changing acceleration

If you modify the Proportional/inversely proportional part, into an exponential equation, and you modify the mass, you could effectively do something of (object mass of almost zero), times a large amount of force = massive acceleration ( which is increased due to an exponential amount, maybe in the order of 10, because why not.)

**so conclusion **

you are the basically taking a person, who would weigh in at 80kg, reduced to 0.00000....01, milligrams, and apply a force of say a pound of C4 explosive. the acceleration would be massive, and once the force has dissipated, you have changed the mass again to say 8000kg while keeping the speed, and therefore the momentum.


If he can make himself very light for a brief moment, he could seriously reduce the damage from impact at the end of a fall. So, he could leap off a building and be very light just at the moment he hits, and the impact would be seriously reduced. Probably he could do something similar in a car crash, assuming he isn't crushed etc. by parts of the car. It's the old "sponge rubber brick" trick.


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