A pebble is thrown vertically upwards with a speed of 20 m s-2. How high will it be after 2 s ? (Take g = 10 m s-2)

Time (t) = 2 s

g = 10 m s^-2

Initial velocity (u) = 20 m s^-2

As we know, the equation of motion

h = ut – 1/2 gt² (a = -g, as movement is against gravity)

= 20 × 2 – 1/2 × 10 × 2²

= 40 – 5 × 4

= 40 – 20

= 20 m

Hence, greatest height reached by the ball = 20 m