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When an object is dropped or thrown downward, the distance, d , that it falls in time, t is described by the following equation:

s = 5 t 2 + v 0 t

In this equation, v 0 is the initial velocity, in m · s - 1 . Distance is measured in meters and time is measured in seconds. Use the equation to find how far an object will fall in 2 s if it is thrown downward at an initial velocity of 10 m · s - 1 .

  1. We are given an expression to calculate distance traveled by a falling object in terms of initial velocity and time. We are also given the initial velocity and time and are required to calculate the distance traveled.

    • v 0 = 10 m · s - 1
    • t = 2 s
    • s = ? m
  2. s = 5 t 2 + v 0 t = 5 ( 2 ) 2 + ( 10 ) ( 2 ) = 5 ( 4 ) + 20 = 20 + 20 = 40
  3. The object will fall 40 m in 2 s if it is thrown downward at an initial velocity of 10 m · s - 1 .

When an object is dropped or thrown downward, the distance, d , that it falls in time, t is described by the following equation:

s = 5 t 2 + v 0 t

In this equation, v 0 is the initial velocity, in m · s - 1 . Distance is measured in meters and time is measured in seconds. Use the equation find how long it takes for the object to reach the ground if it is dropped from a height of 2000 m. The initial velocity is 0 m · s - 1 .

  1. We are given an expression to calculate distance travelled by a falling object in terms of initial velocity and time. We are also given the initial velocity and distance travelled and are required to calculate the time it takes the object to travel the distance.

    • v 0 = 0 m · s - 1
    • t = ? s
    • s = 2000 m
  2. s = 5 t 2 + v 0 t 2000 = 5 t 2 + ( 0 ) ( 2 ) 2000 = 5 t 2 t 2 = 2000 5 = 400 t = 20 s
  3. The object will take 20 s to reach the ground if it is dropped from a height of 2000 m.

Investigation : mathematical modelling

The graph below shows how the distance travelled by a car depends on time. Use the graph to answer thefollowing questions.

  1. How far does the car travel in 20 s?
  2. How long does it take the car to travel 300 m?

A researcher is investigating the number of trees in a forest over a period of n years. After investigating numerous data, the following data model emerged:

Year Number of trees in hundreds
1 1
2 3
3 9
4 27
  1. How many trees, in hundreds, are there in the SIXTH year if this pattern is continued?
  2. Determine an algebraic expression that describes the number of trees in the n t h year in the forest.
  3. Do you think this model, which determines the number of trees in the forest, will continue indefinitely? Give a reason for your answer.
  1. The pattern is 3 0 ; 3 1 ; 3 2 ; 3 3 ; . . .

    Therefore, three to the power one less than the year.

  2. y e a r 6 : 3 5 h u n d r e d s = 243 h u n d r e d s = 24300
  3. n u m b e r o f t r e e s = 3 n - 1 h u n d r e d s
  4. No

    The number of trees will increase for some time. Yet, eventually the number of trees will not increase any more. It will be limited by factors such as the limited amount of water and nutrients available in the ecosystem.

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Source:  OpenStax, Siyavula textbooks: grade 11 maths. OpenStax CNX. Aug 03, 2011 Download for free at http://cnx.org/content/col11243/1.3
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