Question

Dear sir,

Please help me with this questions.

1) An object is suspended with a string which gets streched. When the object is completely immersed in water, the extension of string decreases. explain why it happens?

2) A rocket can move in airfree space but a jetplane cannot. Why?

Thank you & Best Regards,
Adwaith

Answer 1

(1). The extension of string reduces because when the object is immersed in water,it loses weight due to the upthrust exerted by water. So, the strecthness of the thread while it is suspended in the water decress but increase in air.

(2). A rocket is self-reliant, as inside the rocket both the fuel and the oxygen needed to burn the fuel are available.
Therefore, a rocket can move in air free space.
On the other hand, jet has fuel only.
It takes oxygen from the atmosphere to burn the fuel.
Hence, a jet plane cannot operate in air free space.