The driver suddenly applied the brakes.
Any sudden brake loss can be the cause of 1. brake line damage 2. master cylinder disfunction
Inertia
Because you are decelerating sharply
NO
Brakes.
You probably need to change your back brakes.
The bike brakes locked up suddenly while riding due to a malfunction or issue with the brake system, such as a mechanical failure, worn brake pads, or debris obstructing the brake mechanism.
If all the passengers are properly buckled in and the car brakes suddenly to a stop, someone may spill their coffee.
passenger were hitched when the bus driver suddenly applied the brakes
You have a very serious and dangerous problem. More than likely the master cylinder if about to completely fail. When it does fail you will have no brakes at all. Have this repaired yesterday.
Suddenly applying the brakes on a wet or icy road could cause the wheels to lock. With the wheels locked up it takes longer to stop. Also, locked wheels could lead to a loss of control of the vehicle.