Two balls, A and B, are thrown simultaneously, A vertically upward with a speed of 20 m/s from the ground and B vertically downward from a height of 40 m with the same speed and along the same line of motion. At what points do the two balls collide by tak

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Q: 82 (NDA-II/2016)
Two balls, A and B, are thrown simul¬taneously, A vertically upward with a speed of 20 m/s from the ground and B vertically downward from a height of 40 m with the same speed and along the same line of motion. At what points do the two balls collide by taking acceleration due to gravity as 9-8 m/s*?

question_subject: 

Logic/Reasoning

question_exam: 

NDA-II

stats: 

0,1,7,4,2,2,0

keywords: 

{'acceleration': [0, 0, 2, 8], 'balls': [0, 1, 1, 0], 'gravity': [0, 0, 0, 6], 'height': [0, 0, 1, 2], 'motion': [0, 0, 0, 3], 'ground': [2, 1, 4, 17], 'same speed': [0, 0, 1, 3], 'speed': [0, 1, 2, 0]}

Option 1: The balls will collide after 3s at a height of 30-2 m from the ground.

This option is incorrect. The balls are thrown with the same speed in opposite directions, so they will meet at a point between their initial positions. It is assumed that the positive direction is upward, so the collision point will be at a higher position than the initial position of ball B (which is 40m above the ground).

Option 2: The balls will collide after 2s at a height of 20`1 m from the ground.

This option is incorrect. The collision point will be higher than the initial position of ball A (which is 0m above the ground).

Option 3: The balls will collide after 1s at a height of 151 m from the ground.

This is the correct option. Since the balls have the same initial speed and opposite directions, they will meet after the same amount of time it takes for ball A to reach its highest point. It takes 1 second for ball A to reach its highest point, which is 20 meters above the ground. Therefore, the collision point will be 20m above the ground.

Option 4: The balls will collide after 5s at a