When a ball is dropped into a lake from a height 4.9 m above the water level, it hits the water with a velocity v and then sinks to the bottom with the constant velocity v. It reaches the bottom of the lake 4.0 s after it is dropped. The approximate depth of the lake is :

Question

When a ball is dropped into a lake from a height 4.9 m above the water level, it hits the water with a velocity v and then sinks to the bottom with the constant velocity v. It reaches the bottom of the lake 4.0 s after it is dropped. The approximate depth of the lake is : (A) 19.6 m (B) 29.4 m (C) 39.2 m (D) 73.5 m

Tardigrade Admin · Accepted Answer

V 2=2 × 9.8 × 4.9 V =9.8 m / s Depth = distance travelled in 3 seconds =9.8 × 3=29.4 m

Q. When a ball is dropped into a lake from a height $4.9 m$ above the water level, it hits the water with a velocity $v$ and then sinks to the bottom with the constant velocity v. It reaches the bottom of the lake $4.0 s$ after it is dropped. The approximate depth of the lake is :

$19.6 m$

$29.4 m$

$39.2 m$

$73.5 m$

$V^{2} = 2 \times 9.8 \times 4.9$
$V = 9.8 m / s$
Depth $=$ distance travelled in $3$ seconds
$= 9.8 \times 3 = 29.4 m$

Q. When a ball is dropped into a lake from a height 4.9m above the water level, it hits the water with a velocity v and then sinks to the bottom with the constant velocity v. It reaches the bottom of the lake 4.0s after it is dropped. The approximate depth of the lake is :

19.6m

29.4m

39.2m

73.5m