# In order to help an isolated village, a stationary helicopter releases boxes of food supplies from a height h A = 50 m. Each box is provided with a parachute.

## Presentation on theme: "In order to help an isolated village, a stationary helicopter releases boxes of food supplies from a height h A = 50 m. Each box is provided with a parachute."— Presentation transcript:

In order to help an isolated village, a stationary helicopter releases boxes of food supplies from a height h A = 50 m. Each box is provided with a parachute. The set (S) [box, parachute] has a mass M = 50 kg. (S), released at A without initial velocity (V A = 0), moves down along the vertical trajectory ABC and reaches B, of height h B = 45 m, with a speed V B = 10 m/s. 1) All the forces of friction are neglected while falling from A to B.The mechanical energy of (S) is conserved along the path from A to B. Why? P.E reference Mechanical energy is conserved because no friction along AB. 2) Specify the transformation of energy that takes place while falling from A to B. As it starts to fall the potential energy begins to be transformed into kinetic energy.

In order to help an isolated village, a stationary helicopter releases boxes of food supplies from a height h A = 50 m. Each box is provided with a parachute. The set (S) [box, parachute] has a mass M = 50 kg. (S), released at A without initial velocity (V A = 0), moves down along the vertical trajectory ABC and reaches B, of height h B = 45 m, with a speed V B = 10 m/s. 3) Upon reaching B, the parachute opens and the set (S) continues its fall at a constant speed of 10m/s until it reaches C (V C =10 m/s). Find the decrease in the mechanical energy of (S) when it passes from B to C.

In order to help an isolated village, a stationary helicopter releases boxes of food supplies from a height h A = 50 m. Each box is provided with a parachute. The set (S) [box, parachute] has a mass M = 50 kg. (S), released at A without initial velocity (V A = 0), moves down along the vertical trajectory ABC and reaches B, of height h B = 45 m, with a speed V B = 10 m/s. 4) How does this loss of energy appear? It appears in the form of heat energy (thermal heat) 4) One of the parachutes did not open while falling from A to C. Determine, in this case, the speed with which this box reaches C. Mechanical energy is conserved because no friction along BC then :

5- What can you conclude about the role of the parachute in the fall of the box? The parachute reduces the speed of the box upon impact with the ground.

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