Question

A body is projected downward at an angle of 30° with the horizontal from the top of a building 170 m high. Its initial speed is 40 m/s. 2.49 (c) At what angle with the horizontal will it strike? (c) 60

Answer 1

Answer:

The body will strike at angle 60.46°

Explanation:

Vertical motion of body:

 Initial speed, u = 40sin30 = 20m/s

 Acceleration, a = 9.81 m/s²

 Displacement, s = 170 m

 We have equation of motion, v² = u² + 2as

 Substituting

   v² = 20² + 2 x 9.81 x 170

    v = 61.12 m/s

 Final vertical speed = 61.12 m/s

 Final horizontal speed = initial horizontal speed = 40cos30= 34.64m/s

 Final velocity = 34.64 i - 61.12 j m/s

 Magnitude

     $v=\sqrt{34.64^2+(-61.12)^2}=70.25m/s$

 Direction

      $\theta =tan^{-1}\left ( \frac{-61.12}{34.64}\right )=-60.46^0$

 The body will strike at angle 60.46°