NTA Abhyas JEE Main2020PhysicsMotion in Two DimensionsPractice
A ball is projected at an angle of 30 ° above with the horizontal from the top of a tower and strikes the ground in 5 s at an angle of 45 ° with the horizontal. Find the speed with which it was projected.
Options
- A5 0 3 - 1   m s - 1
- B5 0 2 - 1   m s - 1
- C7 0 3 - 1   m s - 1
- D8 0 3 - 1   m s - 1
Correct answer
A. 5 0 3 - 1   m s - 1
Step-by-step solution
v x = - v y u cos 30 ° = - ( u sin 30 ° - g t ) u 3 2 = - u 2 - 1 0 × 5 u 3 + 1 2 = 5 0 ⇒ u = 1 0 0 1 3 + 1 ⇒ u = 5 0 3 - 1 m s - 1