Question

11. An airplane flies to east at 100 m/s, while a bird flies to west and collides with the airplane. The velocity of the bird is 4 m/s. In the reference frame of the plane, what is the value of the speed of the bird? A) 4 m/s B)100 m/s C)104m/s D) 96 m/s E) 52 m/s 12. When the instantaneous velocity of a car is zero, A) the acceleration should be zero. B) the acceleration should be a constant. C) the acceleration cannot be zero. D) the acceleration cannot be a constant. E) none of above is correct. 13. The velocity of a car is to the east, then A) the acceleration should be to the east. B) the acceleration should be to the west. C) the acceleration should be to the north. D) the acceleration should be to the south. E) none of above is correct. 14. An elevator moves down faster and faster, which implies A) the magnitude of supporting force is smaller than the weight. B) the magnitude of supporting force is greater than the weight. C) the magnitude of supporting force is equal the weight. D) none of above is correct.

Answer 1