Why does a fireperson sometimes struggle when holding the pipe issuing water? Class 9

Why does a fireperson sometimes struggle when holding the pipe issuing water? Class 9

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Question 1.

Why does a fireperson sometimes struggle when holding the pipe issuing water? Class 9

Answer:

According to Newton's third law of motion, when water is expelled from the pipe at high speed in the forward direction, the pipe (and the person holding it) experiences an equal and opposite reaction force in the backward direction. This backward reaction force on the pipe can be large if the water comes out at high speed and in large volume, making it difficult for the fireperson to hold the pipe steady.

Question 2.

Suppose a spacecraft is moving in a region of space where the gravitational force acting upon it is negligible. Suggest how it can change its velocity. Class 9

Answer:

In a region where gravity is negligible, the spacecraft can change its velocity by firing its rocket engine. The engine expels exhaust gases in one direction; by Newton's third law, these gases exert an equal and opposite force on the spacecraft, causing it to accelerate in the opposite direction.

1. To slow down: fire the engine in the direction of motion (exhaust goes forward, spacecraft decelerates).
2. To speed up: fire the engine opposite to the direction of motion.
3. To change direction: fire the engine at an appropriate angle.