Question

The height, h meters, reached by a projectile after t seconds travelling vertically upwards is given by the formula h=70t-16t^2. Calculate t if h is 76 meters.

Answer 1

This is your answer with step by srep explanations
Here,I have splitted ‘-70t’ into
‘-32t &-38t’ they both when added make ‘-70t’ and when multiplied make ‘76x16=1216’

Answer 2

The value of t is 2.0 sec

Step-by-step explanation:

Given that,

Height h = 76

The equation of height  is

$h = 70t-16t^2$

We need to calculate the time

Using given equation of height

$h=70t-16t^2$

Put the value of h in equation (I)

$76=70t-16t^2$

$16t^2-70t+76=0$

Using quadratic formula.

$t=\dfrac{-b\pm\sqrt{b^2-4ac}}{2a}$

Put the value into the formula

$t=\dfrac{70\pm\sqrt{(70)^2-4\times16\times76}}{2\times16}$

$t=2, 2.135$

We will take smaller value of t.

Hence, The value of t is 2 sec.

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Topic : projectile motion

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