Question

A stone is dropped from a balloon moving upwards at 20m/s at a height at 105m.distance travelled by the stone, just before reaching the ground.....
A) 125 . B) 145m. C) 130m. D) 120m

Answer 1

Answer on Question #48631, Physics, Mechanics | Kinematics | Dynamics

A stone is dropped from a balloon moving upwards at $20\mathrm{m/s}$ at a height at $105\mathrm{m}$. distance travelled by the stone, just before reaching the ground...

A) 125. B) 145m. C) 130m. D) 120m

Solution:

$a = g = -10\,m/s^2$ is acceleration.

The distance travelled upward is $(\mathrm{v_f} = 0)/$

$$d_1 = \frac{v_f^2 - v_0^2}{2g} = \frac{0 - 20^2}{-2 \cdot 10} = 20\,\mathrm{m}$$

The distance down is

$$d_2 = d_1 + h$$

Thus, total distance is

$$d = 2d_1 + h = 2 \cdot 20 + 105 = 145\,\mathrm{m}$$

Answer: B) 145m

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