Water ejects with a speed of 0.2 ms-1 through a pipe of area of cross-

1.	Water ejects with a speed of 0.2 ms-1 through a pipe of area of cross-section 1 × 10-2 m2. If the water strikes a wall normally, calculate the force on the wall in newtons, assuming the velocity of the water normal to the wall is zero after the collision.
Answer» Volume of water striking the wall per second = 0.2 × 10^-2 = 2 × 10^-3 m³ Mass of the water striking the wall in one second = volume × density = 2 × 10^-3 × 1000 = 2 kg Change in velocity of water on striking the wall in one second = 0.2 – 0 = 0.2 ms^-1 Force acting on the wall = change in momentum = 2 × 0.2 = 0.4N.

Water ejects with a speed of 0.2 ms-1 through a pipe of area of cross-section 1 × 10-2 m2. If the water strikes a wall normally, calculate the force on the wall in newtons, assuming the velocity of the water normal to the wall is zero after the collision.

Answer»

Volume of water striking the wall per second

= 0.2 × 10^-2 = 2 × 10^-3 m³

Mass of the water striking the wall in one second = volume × density

= 2 × 10^-3 × 1000 = 2 kg

Change in velocity of water on striking the wall in one second

= 0.2 – 0 = 0.2 ms^-1

Force acting on the wall

= change in momentum

= 2 × 0.2

= 0.4N.