Water jet leaves a horizontal nozzle with a velocity of 12 m/s and mass flow rate of 30 kg/sstrikes the vertical wall of a cart moving at a fixed direction. After the strike, the water splatters ofin all directions on the surface of the cart wall. Determine the force which must be applied to thecart to: (a) keep it moving at a constant velocity of 4 m/s, (b) to keep it motionless at a fixed posi-tion. Assume that the density of water is 1000 kg/m3.

a) 160 N

b) 360 N

Explanation:

v = 12 m/s

= 30 kg/s

ρ = 1000 kg/m^3

a) when the water  jet is moving at a constant velocity, then force exerted by the jet in the moving plane,

Fx = ρA(v- 4)^2

=ρAv

30 = 1000*A*12

A=2.5*10^(-3)

Fx = ρA(v-4)

Fx = 1000*2.5*10^(-3)*(12 - 4)^2

Fx = 160 N

b) When water jet striking on a stationary vertical plate, the force in the direction of jet:

Fx = ρAv^2

Fx = 1000*2.5*10^(-3)*12^2

Fx = 360 N

a.) travels faster in solids because the particles are closer together.

air is a gas water is a liquid

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.