physics practice

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physics practice
2013-08-31 06:55:35

practicing for physics
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  1. A parachutist of mass 75 kg jumps from a plane at a height of 4 000 m above sea level.

    (a) The parachutist falls through a distance of 2 400 m during the first 60 seconds. Calculate the average speed of the parachutist during this time.
    • v=∧d/∧t
    • =2400/60
    • =40ms-¹
  2. (b) Explain the vertical motion of the parachutist just after she jumps out of the plane (before the parachute opens). In your answer you should:
    • draw and label the vertical force(s) acting on the parachutist and show their relative sizes on the image to the right
    • describe the net vertical force and state whether the force(s) are balanced or unbalanced
    • describe the vertical motion of the parachutist
    • explain how the net vertical force affects the vertical motion.
    write it down.
  3. (c) After the 60 seconds, the parachutist pulls the cord and opens her parachute. Explain how the parachute reduces the speed of the parachutist when it is just opened. In your answer you should consider:
    • how the motion of the parachutist changes when the parachute is opened
    • the effect of the size of the parachute on the motion
    • the effect of the parachute on the net vertical force.
    When the parachute opens, there is more surface area for air to hit. ∴drag will increase Fdrag>Fgrav. Eventually after time the gravity