7. Two identical objects A and B fall from rest from different heights to the ground. If object B takes twice as long as A to reach the ground, what is the ratio of the heights from which A and B fell? Assume the effect of air resistance is negligible. a. 1: 2 b. 1:2 c. 1:3 d. 1:4 e. 1:8 8. 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 ais zero. b. is directed upwards. c. is directed downwards. d. changes direction from upwards to downwards. e. cannot be determined 9. A hiker walks 6.7 miles to the east in 5.1 hours then turns around and walks 1.1 miles to the west in 1.0 hours. What was the magnitude of her average velocity for the trip? a. 0.92 mph b. 1.3 mph c.1.2 mph d. 3.9 mph 10. Measurements M₁± U₁ and M2 ± U2 can be considered equivalent if a. they agree within 0.01 units b. JM₁-M2<U₁+U₂ c. M₁2+ M2²=U₁² + U₂² d. they have the same number of significant figures e. none of the above