179- A stone is thrown vertically upward from height $h$ with initial velocity $V_0$ and hits the ground after $4$ seconds. If in the last second of its motion it travels $\dfrac{h}{2}$, how many meters is $h$? $\left(g = 10\,\dfrac{\text{m}}{\text{s}^2}\right)$

• [(1)] $60$
• [(2)] $90$
• [(3)] $120$
• [(4)] $180$

%% Page 16 Physics 120-C Page 15

From the top of a 64 metres high tower, a stone is thrown upwards vertically with the velocity of $48 \mathrm {~m} / \mathrm { s }$. The greatest height (in metres) attained by the stone, assuming the value of the gravitational acceleration $g = 32 \mathrm {~m} / \mathrm { s } ^ { 2 }$, is:
(1) 112
(2) 88
(3) 128
(4) 100

From the top of a tower, a ball is thrown vertically upward which reaches the ground in 6 s . A second ball thrown vertically downward from the same position with the same speed reaches the ground in 1.5 s . A third ball released, from the rest from the same location, will reach the ground in $\_\_\_\_$ s.

Q2. A body projected vertically upwards with a certain speed from the top of a tower reaches the ground in $t _ { 1 }$. If it is projected vertically downwards from the same point with the same speed, it reaches the ground in $t _ { 2 }$. Time required to reach the ground, if it is dropped from the top of the tower, is :
(1) $\sqrt { t _ { 1 } t _ { 2 } }$
(2) $\sqrt { t _ { 1 } + t _ { 2 } }$
(3) $\sqrt { t _ { 1 } - t _ { 2 } }$
(4) $\sqrt { \frac { t _ { 1 } } { t _ { 2 } } }$