Question
1.
2.
3.
4.
The conservation of linear momentum for a control volume is a is zero if there is no mass flow into or out of the control volume, is zero if there are no forces acting on the control volume, is zero under steady-state conditions. is zero if the momentum in to the control volume is balanced by the momentum out of the control volume. A jet of water leaves the nozzle at the end of a hose that is vertical as shown below. A control volume for the nozzle is shown with dotted lines. The weight of the nozzle is negligible. Force is positive in the positive z-direction. The correct statement about the force at the coupling that holds the nozzle in place is. A bent pipe is shown in the horizontal (x-y) plane below. A water flow enters at a velocity V, goes through a 180 degree turn in the horizontal plane, and leaves at the same velocity V. The pipe is supported along the edge as shown. Force is positive in the positive x and y-directions. The correct statement about the magnitude of the force Fx holding the pipe in place is You are floating in a canoe down the Wisconsin river moving with the current. Assume that the flow is steady. Because the flow rate is steady, you do not accelerate as you float down the river. Because the river changes width and depth along its path, you accelerate as you float down the river. You are continuously accelerating since the river is flowing downhill. You will accelerate only if the flow becomes unsteady.
Explanation / Answer
1.(c) under steady state conditions ,there is o variation of anything with time so integral with respect to time is zero. (c)
2.(a) because the pressure at the end of the nozzle is always less than the pressure at the starting as a nozzle converts pressure energy to kinetic energy, force on the nozzle=(P2A2-P1A1)<0 soforce is in the negative z direction and reaction force in the z direction.
3.(c) force is rate of change of momentum, m(-v-v)=-2mv.this is for water. so momentum transferred to pipe is 2mv in the positive x diection.therefore the reaction force must be in negative x direction so (c).
4.(c) this is true because if the floww is steady doesn't mean there is no acceleration. rate of change of momentum causes the force too.
