Two balls are projected from the top of a tower of height 120 m, one with an initial upward velocity of 36 km/h and the other with an initial downward velocity of 36 km/h. The speed of each ball just before hitting the ground is: (take g = 10 m/s2 )
Correct answer: B. 50 m/s, 50 m/s
- A. 50 m/s, 70 m/s
- B. 50 m/s, 50 m/s
- C. 70 m/s, 50 m/s
- D. 50 m/s, 5√2m/s
Explanation
When solving projectile motion problems, the final speed just before hitting the ground is independent of the initial direction of the velocity. Both balls will have the same speed of 50 m/s before hitting the ground due to the height of the tower and the effect of gravity. The correct answer is Option B.
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Displacement, velocity and acceleration describe motion, including the horizontal and vertical components of projectile motion. The chapter connects these quantities with Newton's laws, momentum and impulse, then applies conservation of momentum to collisions, distinguishing elastic collisions from inelastic ones.
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