39. A projectile is launched at an angle of 30° and lands 20 s later at the same

Question

39. A projectile is launched at an angle of 30° and lands 20 s later at the same height as it was launched. (a) What is the initial speed of the projectile? (b) What is the maximum altitude? (c) What is the range? (d) Calculate the displacement from the point of launch to the position on its trajectory at 15 s. 40. A basketball player shoots toward a basket 6.1 m away and 3.0 m above the floor. If the ball is released 1.8 m above the floor at an angle of 60 above the horizontal, what must the initial speed be if it were to go through the basket?

Explanation / Answer

Here,

let the initial speed is u

hi = 1.8 m

y = 3 m

x = 6.1 m

theta = 60 degree

as y = hi + x * tan(theta) -g * x^2/(2 * (u * cos(theta))^2)

3 = 1.8 + 6.1 * tan(60 degree) - 9.8 * 6.1^2/(2 * (u * cos(60 degree))^2)

solving for u

u = 8.82 m/s

the initial speed of the ball is 8.82 m/s

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