An athlete jumps at a speed of 4m/s at an angle of 23°. how long does the athlete stay in the air? a. 0.55s b. 0.75s c. 0.92s

Question

An athlete jumps at a speed of 4m/s at an angle of 23°. how long does the athlete stay in the air?
a. 0.55s
b. 0.75s
c. 0.92s
d. 0.32s​

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Ngọc Hoa 3 years 2021-07-16T17:06:09+00:00 2 Answers 13 views 0

Answers ( )

  1. Dau
    0
    2021-07-16T17:07:29+00:00
    Reply

    We only care about the vertical component of the athlete’s position vector, which at time t is

    y = (4 m/s) sin(23º) t – 1/2 g t²

    where g is the acceleration due to gravity.

    The athlete stays airborne for as long as y > 0, which happens for

    (4 m/s) sin(23º) t – 1/2 (9.80 m/s²) t² > 0

    t (1.56 m/s – (4.9 m/s²) t) > 0

    ==>  0 < t < (1.56 m/s)/(4.9 m/s²)

    ==>  0 < t < 0.319 s

    so the answer is D.

  2. thanhha
    0
    2021-07-16T17:07:55+00:00
    Reply

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