Question

Suppose water comes out of pipe at the rate of 3kg per second and it's velocity changes from 5m/sec to zero on striking the wall perpendicularly the force exerted on the wall is. A 5N. B 10N C 15N D 20N​

Answer 1

Given :

▪ Water comes out of pipe at the rate of 3kgps

▪ Initial velocity = 5mps

▪ Final velocity = zero

To Find :

▪ Force exerted on the wall.

Concept :

✏ This question is completely based on concept of Newton's second law of motion.

✏ As per this law, Force is defined as the rate of change in momentum. (wrt time)

✏ Momentum is defined as the product of mass and velocity.

Calculation :

$\dashrightarrow\bf\:F\times\Delta t=\Delta P\\ \\ \dashrightarrow\sf\:F=\dfrac{\Delta P}{\Delta t}\\ \\ \dashrightarrow\sf\:F=\dfrac{dm}{dt}\times \Delta v\\ \\ \dashrightarrow\sf\:F=3\times 5\\ \\ \dashrightarrow\underline{\boxed{\bf{\green{F=15N}}}}\:\gray{\bigstar}$

Answer 2

$\bigstar$ Given :

Water comes out of pipe at the rate of 3 kg/s

Initial velocity = 5 m/s

Final velocity = 0

Change in velocity = Δv = 5-0 = 5 m/s

$\bigstar$ Explanation :

A/c to Newton second's law ,

" Force is defined as rate of change of momentum "

Momentum , P = mΔv

$\bold{\bf{\red{\implies F=\frac{\Delta P}{\Delta T}}}}\\\\ \implies F=\frac{dm.\Delta v}{dt} \\\\\implies F= \frac{dm}{dt}*\Delta V\\\\ \implies F=3*5\\\\\bold{\bf{\blue{\implies F=15 N}}}$