Intro to Tension Forces – Nerdstudy Physics

Intro to Tension Forces – Nerdstudy Physics


Hey guys! In this lesson, we’re going to learn about
tension forces. That’s the kind of force we see when we
pull on a rope, for example. Alright, so let’s get started! Suppose we’ve got a ball hanging from the
ceiling by a rope. What is keeping the ball from falling to the
floor anyways? After all, gravity is acting on the ball right? Well, it’s the rope that’s keeping the
ball up! So the rope must be applying a force on the
ball to prevent it from falling. We call that force the tension force, because
the rope is being put under tension by the ball. So any force that appears as a result of pulling
on a rope, a string, or anything similar to that is called tension. Actually, we can think of tension forces as
being, in a limited sense, the opposite of normal forces. Now if you don’t remember what a normal
force is, we encourage you to watch our videos on normal forces. Very briefly, we can say that a normal force
occurs when a surface, like a table, resists being compressed by a force. The surface applies a force which prevents
an object from moving into the surface, and we call that the normal force. Tension forces do something quite similar,
except that instead of resisting compression, they resist forces that cause things to stretch. For example, when we hang a ball on a rope,
the rope applies a force to the ball which makes it resist being stretched out. The result is tension. Looking back at normal forces, it seems obvious
that when an object is not pushing against a surface, the normal force must be zero. Tension forces are similar to this, but in
an opposite sense. If an object is not pulling on a rope, the
tension force is zero. Alright, I think we’ve got enough knowledge
to look at a very simple example. Let’s look at the ball on a rope again. If the ball has a mass of 10 kilograms, what
is the tension force? Hmm, how would we solve a question like that? Well, the answer would be 98.1 newtons upward. How did we get that answer? First of all, we have to look at the forces
that are acting on the ball. One of them is obviously gravity. What other forces are there? Well, there’s really only one other force:
the force of tension! More specifically, it’s the tension force
being applied by the rope onto the ball. And since the ball isn’t moving, the forces
must cancel out. So our next step will be to find the force
of gravity on the ball. Cool! To find the force of gravity, in other words
the weight, we’ll need to use Newton’s Second Law. We already know the mass of the ball, which
is 10 kilograms. As for the acceleration, that’s constant
near the Earth’s surface which is 9.81 meters per second squared downward. And once we substitute those values into the
equation, we’d get 98.1 newtons downward for the weight of the ball. And since the gravitational force must be
cancelled by the tension of the rope, we find that the tension force being applied by the
rope on the ball is 98.1 newtons upward. Awesome! Alright, that brings us to the end of this
video on the Introduction to Tension! In our next video, we’re going to talk about
idealized ropes with properties like zero mass. And we’re going to also see how that might
simplify our calculations. So, we hope to see you in the next video,
and until then, have a good one!

16 comments

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