Hello everyone and welcome to JAMA KELF. In this example we have you are standing behind a truck and suddenly the truck starts moving forward. Now what you observe is a pendulum hanging behind the truck swiss to the back because of its inertia. So the question is using this scenario can you determine the acceleration of the car. So what do we have? We have a rope, a pendulum of mass M, hanging downwards. It makes an angle theater and the whole system is moving forward. So let's draw the free body diagram on the mass. The weight obviously acts vertically downwards. The tension in the string acts along the string and upwards. This angle right here is theater so we can resolve the tension in the string in the two components. This will be T, sine theater and this will be T, cosine theater. Now the system is moving forward. So what this means is that the sum of forces along the wide direction this is T, cosine theater minus Mg. This will be equal to zero and this means that T cosine theater is equal to Mg. In other words T is equal to Mg divided by cosine theater. This is the value of the expression for T. Now on the other hand the sum of forces along the x-direction is equal to Mg which would mean that T, sine theater is equal to Mg. But what is T? T is Mg divided by cosine theater and we are multiplying this by sine theater all equal to Mg. The M's conglomerate cancel sine over cosine is tangent. So this implies that the acceleration of the curve is given by G, the tangent of theater. Yes it's possible for you to measure the acceleration of the curve without actually going outside of the curve without really going outside of the curve.