Answer to Question #210245 in Mechanics | Relativity for han

Question

A parachute opens during the spacecrafts descent through the atmosphere.

Figure 2 shows the parachute spacecraft system with the open parachute displacing the atmospheric gas. This causes the system to decelerate.

Explain with reference to newtons laws of motion why displacing the atmospheric gas causes a force on the system and why this force causes the system to decelerate

Answer 1

Explanations & Calculations

• Consider a moment during the motion of the parachute.

• It travels down and the atmospheric gas is in contact with it all the time.
• Those layers of air that come into contact with the parachute are stationary compared to their behavior just after contacting with the parachute as they are moved \displaced at the speed of the parachute.
• This action on the gas make their momentum to change.
• Change in momentum (during a lesser time actually) impose a huge force on it. This conforms to the Newton's first law
• This huge force in return, is applied on the parachute at the same magnitude & the opposite direction conforming to the Newton's third law.
• That is why displacing air imposes a force on the system.

• And why that force puts the system in deceleration is because it acts along the opposite direction to the direction parachute is moving.
• That force is larger than the sytems's own weight which at the moment acting towards the ground.
• Then a net force is along upwards.
• Then conforming to the Newton's second law there is an acceleration generated.
• But that acceleration is upwards but a deceleration when considered with respect to the system's view\sense.