Final answer:
Passengers move forward in a sudden stop and slide to the side in sharp turns due to inertia, as per Newton's first law. Safety features like seat belts and airbags minimize the effects by increasing the time over which the stopping force acts.
Step-by-step explanation:
When a car stops suddenly or makes a sharp turn, the passengers experience what feels like a force moving them forward or sideways. This is due to inertia, which is a property of mass that resists changes in motion. According to Newton's first law, an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. Hence, when the car stops suddenly, passengers tend to move forward relative to their seats. This is because the car's brakes apply a force to the car, stopping it, but the passengers inside the car continue to move at the original speed (inertia). This effect is minimized by safety features like seat belts and airbags that increase the time over which the stopping force acts, thereby reducing the force.
Similarly, when a car makes a sharp turn, the passengers tend to slide to one side due to their body's inertia wanting to keep moving in a straight line while the car changes direction. This sensation of sliding sideways is sometimes mistaken for a centrifugal force, but it's actually just the passenger's tendency to continue in a straight line as the car turns. There is no real sideways force acting on the passengers, but rather it is the car that is exerting a force to change direction. These situations illustrate the importance of understanding inertia and Newton's laws of motion in providing safe vehicle designs and improving the comfort and safety of passengers.