A stone is thrown with an initial speed of 4.9 m / s from a bridge in vertically upward direction. It falls down in water after 2 sec. The height of bridge is

Question

A stone is thrown with an initial speed of 4.9 m / s from a bridge in vertically upward direction. It falls down in water after 2 sec. The height of bridge is (A) 24.7 m (B) 19.8 m (C) 9.8 m (D) 4.9 m

Tardigrade Admin · Accepted Answer

Here: Initial velocity u=-4.9 m / s (-ve is due to vertically upward motion) Total time t=2 sec The height of the bridge is given by s =u t+(1/2) g t2 =-4.9 × 2+(1/2) × 9.8 ×(2)2 =-9.8+19.6=9.8 m

Q. A stone is thrown with an initial speed of $4.9 m / s$ from a bridge in vertically upward direction. It falls down in water after $2 sec$ . The height of bridge is

24.7 m

19.8 m

9.8 m

4.9 m

Here: Initial velocity $u = - 4.9 m / s$ (-ve is due to vertically upward motion)
Total time $t = 2 sec$
The height of the bridge is given by
$s = u t + \frac{1}{2} g t^{2}$
$= - 4.9 \times 2 + \frac{1}{2} \times 9.8 \times (2)^{2}$
$= - 9.8 + 19.6 = 9.8 m$

Q. A stone is thrown with an initial speed of 4.9m/s from a bridge in vertically upward direction. It falls down in water after 2sec. The height of bridge is