Laws of Motion

Question : 28

Total: 40

A stream of water flowing horizontally with a speed of 15ms–1 gushes out of a tube of cross-sectional area 10–2m2, and hits a vertical wall nearby. What is the force exerted on the wall by the impact of water, assuming it does not rebound?

Solution:

Here, v=15ms–1
Area of cross section, A=10–2m2,F=?
Volume of water pushing out per second =A×v=10–2×15m3s–1
As density of water is 103kgm−3 therefore, mass of water striking the wall per second is
m=(15×10–2)×103=150kg s–1
As F=

change in linear momentum

time

∴F=

m×v

150×15

=2250 N

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