Question

A water tanker filled upto 2/3 of its height is moving with a uniform speed. On sudden application of the brake ,the water in the tank would a). move backward b). move forward c). be unaffected d). rise upwards

Answer 1

The correct answer is the option b - Moves forward.

This may be due to inertia. All objects in a system are in the same state of motion.

So, when a tanker is filled with water up to 2/3rd level, the water inside the tanker is at the same velocity as that of the tanker. So, it stays steady. However, when the tanker's brakes are applied, the velocity of the tanker becomes less but there is no external force acting directly on the water. So, the velocity of the tanker decreases but the velocity of the water inside remains as before. So, the water tends to push itself forward towards the wall of the tanker.

Answer 2

The water in the tank would move forward. An object in motion tends to stay in motion. The brakes stopped the truck but not the water. The kinetic energy from the water didn't go away when the brakes were applied. It is similar to slamming the brakes in your car. Your body moves forward and you need the seatbelt to stop you.