Question 105: Properties of Matter

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 :

Accepted Answer

$${t_1} = \sqrt {{{2h} \over g}} $$
$$ = \sqrt {{{2 	imes 4.9} \over {9.8}}}  = 1\,s$$
$$\Delta t = 4 - 1 = 3\,s$$,
$$v = \sqrt {2gh}  = \sqrt {2 	imes 9.8 	imes 4.9}  = 9.8$$ m/s
$$	herefore$$ depth $$ = 9.8 	imes 3 = 29.4$$ m

Answer

19.6 m

Answer

29.4 m

Answer

39.2 m

Answer

73.5 m

Properties of Matter

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 :

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