A Level Physics Practice Exam

What is the formula to find the energy stored in a string from the applied force?

1. E = F / (2 * deltaL)

2. E = (1/2) * k * deltaL

3. E = (1/2) * F * deltaL

4. E = F * k * deltaL

The correct answer is: E = (1/2) * F * deltaL

The formula to find the energy stored in a string due to an applied force involves understanding how materials stretch and how work is done during that process. When a force is applied to a string, it causes the string to extend. The energy that is stored in the string (or any elastic material) can be derived from the work done on the string as it is stretched. The correct formula for the energy stored (E) involves using the concept of work done, which is the product of the force applied (F) and the displacement (deltaL) the string undergoes while the force is gradually applied. However, it’s essential to note that the force is not constant throughout the stretching process; it increases from zero to the maximum value F. Therefore, the average force can be taken as F/2 during the extension. This leads us to the formula: \[ E = \text{average force} \times \text{displacement} = \frac{F}{2} \times \deltaL. \] This relationship shows how much energy gets stored in the string when subject to an applied force resulting in a displacement, making this formula the appropriate choice for calculating the stored energy under such conditions. Thus, the correct representation of the