1. Tardigrade
  2. Question
  3. Physics
  4. A ball is projected upwards from the top of the tower with a velocity 50 ms-1 making an angle 30° with the horizontal. The height of tower is 70 m. After how many seconds the ball will strike the ground?

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Q. A ball is projected upwards from the top of the tower with a velocity $50\, ms^{-1}$ making an angle $30^{\circ}$ with the horizontal. The height of tower is $70\, m$. After how many seconds the ball will strike the ground?

Motion in a Plane

Solution:

image
$\overline{ Y }=\overline{ v }_{ y } t +\frac{1}{2} \overline{ a }_{ y } t ^{2}$
$70=-\left(50 \sin 30^{\circ}\right) t+\frac{1}{2} \times 10 \times t^{2}$
$70=-25 t+5 t^{2}$
or $t^{2}-5 t-14=0$
$\Rightarrow t=-2 \sec$
or $t=7$ sec. (-ve time is not possible)