A stone is dropped from rest from the top of a 45 m high tower. At the same instant, another stone is projected vertically upward from the ground with a speed of 30 m/s. Neglect air resistance and take g = 10 m/ $s^2.$ After what time do the two stones meet?
Options

Question

A stone is dropped from rest from the top of a 45 m high tower. At the same instant, another stone is projected vertically upward from the ground with a speed of 30 m/s. Neglect air resistance and take g = 10 m/ $s^2.$ After what time do the two stones meet?

Options

G1 Physics · Accepted Answer

Taking upward as positive from the ground, the lower stone has position y1 = 30t - 5 t 2 . t^2. t 2 . The upper stone has position y2 = 45 - 5 t 2 . t^2. t 2 . At meeting, y1 = y2, so 30t - 5 t 2 t^2 t 2 = 45 - 5 t 2 , t^2, t 2 , giving 30t = 45 and t = 1.5 s. Hence, option B is correct.

A stone is dropped from rest from the top of a 45 m high tower. At the same instant, another stone is projected vertically upward from the ground with a speed of 30 m/s. Neglect air resistance and take g = 10 m/ s 2 . s^2. s 2 . After what time do the two stones meet?