Question

An object thrown vertically upward reaches a height of 500 m what was its initial velocity how long will the object take to come back to the earth assume G is equal to 10 M per second square

Answer 1

Given : The distance = s = 500m             Acceleration due to gravity = g = 10m/s²             a = -g               a = -10For the upward motion of the object final velocity = v = 0To Find : Initial velocity = u = ?                Time taken by object to come back = 2t = ?Solution : By Newtons third equation of motion        v² = u² + 2as    ∴ 0² = u² + 2(-10 × 500)    ∴ 0 = u² - 20 × 500    ∴ 0 = u² - 10000    ∴ u² = 10000    ∴ u = √10000    ∴ u = 100By Newton's second equation of motion     s = ut + 1/2 at²  ∴ s = 0 × t + 1/2 10 t²  ∴ 500 = 0 + 5t²  ∴ 500 = 5t²  ∴ t² = 500/5  ∴ t² = 100 ∴ t = √100  ∴ t = 10∴ Total time taken = 2t                               = 2 × 10                               = 20s