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AP EAMCET20227 Jul 2022Evening ShiftPhysicsMotion in Two DimensionsActual

A ball is thrown upward from the top of a building at an angle of 30^ to the horizontal and with an initial speed of 20 ~ms ⁻¹ . If the ball strikes the ground after 3 ~s . then the height of the building is (acceleration due to gravity =10 ~ms ⁻¹ )

Options

  1. A10 ~m
  2. B15 ~m
  3. C20 ~m
  4. D25 ~m

Correct answer

B. 15 ~m

Step-by-step solution

Given situation is shown below Here we are considering only vertical motion of ball. Given, initial vertical velocity of ball aligned u_y & =u =20 30^ & =20 1 2 =10 ~m / s aligned Vertical acceleration, a_y=g=-10 ~m / s ^2 Time to reach the ground =3 ~s . Now using, h=u_y t+ 1 2 a_y t^2 We get, h=10 3+ 1 2 (-10) 3^2 h=30-45=-15 ~m . So height of building is 15 ~m . (negative sign shows downward displacement of ball).

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