A projectile is fired form the top of a 40 m high cliff with an initial speed of 50 m/s at an unknown angle. Find its speed when it hits the ground.

Explanation

To find the speed of the projectile when it hits the ground, we can use the work-energy theorem. Here’s a step-by-step solution:

### Step 1: Understand the Problem
We have a projectile fired from the top of a 40 m high cliff with an initial speed of 50 m/s at an unknown angle. We need to find the speed at which it hits the ground.

### Step 2: Apply the Work-Energy Theorem
According to the work-energy theorem:
\[ \text{Work done by all forces} = \text{Change in kinetic energy} \]
...