When a moving bus suddenly applies brakes, the passengers sitting in it fall forward. This can be explained by Newton’s first law of motion, also known as the law of inertia. This law states that an object in motion will remain in motion with the same speed and direction unless acted upon by an external force. When the bus abruptly stops, the passengers, who were previously moving forward with the bus, continue to move forward due to their inertia. However, the bus provides the external force that abruptly halts their forward motion, causing them to fall forward. This phenomenon is commonly experienced in vehicles when sudden deceleration occurs, highlighting the fundamental principle of inertia described by Newton’s first law of motion.