rt A: ultiple choice questions: You and a friend throw two rocks off a bridge. Y

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rt A: ultiple choice questions: You and a friend throw two rocks off a bridge. Your friend throws hers with an initial direction 30 below the horizontal. You throw yours with the same initial speed but in a direction 302 above the horizontal. When the two rocks hit the water 1. a) your friend's is moving faster. b) they are moving at the same speed. c) yours is moving faster. A stone is thrown vertically upwards, reaches a highest point, and returns to the ground. When the stone is at the top of its path, its acceleration 2. A) is directed downwards. B) is directed upwards. C) is zero. D) changes direction from upwards to downwards. Vector A has length 2 units and directed to the north. Vector B has length 5 units and is directed to the south. Calculate the magnitude and direction of A- 3. A) 3 units, north B) 7 units, south C) 7 units, north D) 3 units, south © 2016 Pearson Education, Inc.

Explanation / Answer

1) from conservation of energy both are thown from the same height and with same velocity so both stones are hitting with the same speed

2) at the highest point velocity is zero and acceleration is due to grvity

so acceleration is acting vertically downwards

3) a = 2j

b = -5j

a-b = sqrt(a^2+b^2+2abcos180) = 3 units north

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