Video Transcript
How much force is applied to an
object of mass five kilograms that is accelerated by that force at a rate of two
metres per second squared?
So in this question, we’ve got
an object which has a mass — let’s say 𝑚 — of five kilograms and is accelerated
— let’s say it’s accelerated to the right — because we can randomly choose a
direction. And we’ve been told that this
acceleration, which we’ll call 𝑎, is two metres per second squared. We’ve been asked to find the
force applied to this object.
Now because the acceleration
we’ve said is to the right, this must mean that the force exerted is also to the
right, since the force and acceleration must be in the same direction. And we’ll call this force
𝐹.
Now to find the value of this
force, we need to recall Newton’s second law of motion. This law tells us that the net
force on an object, 𝐹, is equal to the mass of that object multiplied by the
acceleration it experiences. So with this equation, we’ll be
able to find the net force on the object. And this is exactly what we’ve
been asked to find. Even though the question
doesn’t necessarily say find the net force, we’ve been asked to find how much
force is applied to an object.
Now this may imply that there’s
only one force acting on the object, in which case that force is the net force
anyway. Or there could be multiple
forces acting on the object, but the resultant force or the net force is going
to be a combination of all of those forces, whilst accounting for the direction
in which they act. And that overall combination
can also be thought of as the amount of force applied to an object. And so we can use Newton’s
second law of motion to find our answer to this question.
We can therefore say that the
force on the object, the net force, is equal to the mass, which is five
kilograms, multiplied by the acceleration of the object, which is two metres per
second squared. Now taking a quick look at the
units, we see that we’ve got kilograms and metres per second squared. And those are the base units of
mass and acceleration, respectively. Therefore, when we find our
final answer for the force, it’s going to be in its own base unit as well.
Now the base unit of force is
the newton, which is equivalent to a kilogram multiplied by metres per second
squared. And so when we evaluate our
answer — that’s five kilograms multiplied by two metres per second squared — we
find that the force is 10 kilograms metres per second squared or 10 newtons. And hence, our answer to this
question is that the force applied to this object is 10 newtons.
