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Homework Help: Newton's first law and projectiles questions

  1. Apr 3, 2014 #1
    I just don't get these questions...please help.
    () are what I think the answers are but I am not positive.
    Question set 1:
    Beginning from rest, Mia Edwards runs the 200 meter dash with an acceleration of 0.9 m/s2.
    1. define inertia. (inertia- the tendency of an object to resist change)
    2. what happens to Mia's velocity if acceleration is non-zero and in the same direction as her velocity? (if her acceleration is non-zero and in the same direction as her velocity than her velocity will increase.)
    3. what is the highest velocity Mia reaches after 5 seconds? (4.5 m/s2)
    4. the world record for the 200 meter race is 21.34 seconds. does she break the world record?
    5. what would be the break down? acceleration second by second?
    Question set 2:
    Luke is an archer in the war. Using a bowl, he fires an arrow at 100 feet per second (fps) at 55 degrees above the horizontal ground.
    1. what parts of a triangle are used for sine? what parts of a triangle are used for cosine? (to calculate sine on a triangle you divided the opposite by the hypotenuse. Cosine is calculated with the adjacent divided by the hypotenuse.
    2. what should happen to arrow's vertical velocity as it comes down if gravity works in the same direction? (it gravity works in the same direction as the arrows then the vertical velocity of the arrow will increase.)
    3. How long is the arrow in the air for in total?
    4. Luke’s target is 613 feet away. Will he hit it?
  2. jcsd
  3. Apr 3, 2014 #2

    Simon Bridge

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    i.e. how long would it take mia to run 200m given the information so far?

    ... well, what happens to the acceleration?

    Presumably Luke uses a bow, not a bowl?

    Time to go from the ground, to it's highest point, back to the ground again?
    The speed when it hits the ground is the same as the initial speed.
    You need to divide the motion into horizontal and vertical components to work this out.

    ... you need to do (3) first. What is the horizontal acceleration?
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