4.4.2. Momentum Conservation Equation Application

Try these first

1. 1.

   What does mass conservation imply in a fluid system?

   Hint

   Think about how fluid flows in and out of a container.

2. 2.

   Define momentum in your own words.

   Hint

   Consider how fast an object is moving and how heavy it is.

3. 3.

   What does the mass conservation principle state?

   • Mass can disappear
   • Mass in equals mass out
   • Mass is always increasing

   Hint

   Relate it to fluid flowing in and out of a system.

4. 4.

   True or False: Momentum is conserved in a closed system.

   • True
   • False

   Hint

   Think about Newton's laws.

5. 5.

   A water jet with a cross-sectional area of 10 cm² and velocity of 25 m/s strikes a flat plate. Calculate the force exerted if the density of water is 1000 kg/m³.

   Hint

   Use the formula for mass flow rate and then apply it to find the force.

6. 6.

   A spacecraft has a mass of 20000 kg and is descending at 400 m/s. If it expels gas at 75 kg/s with a velocity of 3000 m/s relative to itself, calculate the thrust and acceleration.

   Hint

   Use the thrust calculation to determine how quickly the spacecraft decelerates.