### Video Transcript

A body weighing 240 newtons is attached at point π΅ by a string whose other end is
fixed to a point π΄ on a vertical wall. The length of the string π΄π΅ is 30 centimeters. The body is also pulled by a horizontal string attached from point π΅ until point π΅
is 18 centimeters away from the wall. Determine the tensions π sub one in the horizontal string and π sub two in string
π΄π΅.

In order to answer this question, we can begin by drawing a simple diagram that
represents the scenario.

First, we have this body attached at point π΅ by string, where the end of the string
is attached to a vertical wall at point π΄. The downwards force of the weight of the body is 240 newtons, and this acts
vertically downwards like so. The string is 30 centimeters. And then we have this second piece of string attached horizontally to the wall. Letβs say it meets at point πΆ at a distance of 18 centimeters. There will be tensional forces keeping this system in place. The first is defined as π sub one and that acts in the horizontal direction and π
sub two in the string π΄π΅.

Notice that what weβve created is a triangle. This means that we can think about this system as a triangle of forces, and we can
use the triangle of forces rule. In the triangle of forces rule, the magnitudes of the forces are proportional to the
side lengths of the triangle. In other words, πΉ sub one over π΄π΅ equals πΉ sub two over π΅πΆ, which equals πΉ sub
three over π΄πΆ. This means that if we can establish the length of the third side in the triangle and
then use the weight force, we should be able to calculate the magnitudes of π sub
one and π sub two.

In fact, since the triangle is right-angled, we can use the Pythagorean theorem or
Pythagorean triples to find the length π΄πΆ. π΄πΆ squared plus π΅πΆ squared equals π΄π΅ squared. That means π΄πΆ squared plus 18 squared equals 30 squared. Subtracting 18 squared from both sides and taking the positive square root and π΄πΆ
equals root 30 squared minus 18 squared, which equals 24. Hence, π΄πΆ is 24 centimeters.

So, now that we have the lengths of the triangle, how do we find the forces? The system is in equilibrium, and we know that the force with a magnitude of 240
newtons acts in the same direction as the length π΄πΆ. Using the triangle of forces rule, we can say that the ratio of this force and the
length of the triangle π΄πΆ is 240 over 24. Thatβs 10. This must be equal to the ratio of π sub one and the horizontal length of 18
centimeters. So, π sub one over 18 equals 10.

Multiplying through by 18 and we find that π sub one equals 180 newtons. We repeat this for the final force. So, π sub two over 30 equals 10. Multiplying through by 30 and we find that π sub two equals 10 times 30, which is
300. Hence, π sub one equals 180 newtons and π sub two equals 300 newtons.