which of the following statements concerning the motion of a body is/are correct?
1)A body has no acceleration whien it is moving with a uniform velocity.
2)A body can have zero velocity but also be accelerating.
3)A body can have a constant speed but a varying velocity.
A.(1)only
B.(3)only
C.(1) and (2)only
D,(2) and (3)only
E,(1),(2) and (3)
答案係米E??
M.C!!~~~
2006-11-05 5:06 am
回答 (3)
2006-11-05 7:27 am
✔ 最佳答案
答案一定係E. (By Y.Y)1) With constant velocity, an object must have zero acceleration.
acceleration=change in velocity over time
As V is constant, change in v=0. So a must be zero.
2) Give an example to you.
When an object is thown upwards and reaches the top,
the velocity is zero. However, the object is still affect
by the gravity with an 10/s-2 acceleration to the ground.
3) Speed is scalar. That means it does not concerned with the direction of motion.
But velocity is vector which concerning the direction of motion.
Therefore, constant speed is not equals the velocity
as the direction of motion may varies.
2006-11-05 5:16 am
我覺得係A。
2006-11-05 5:10 am
應該係 E..........
2006-11-04 21:15:06 補充：
1) When velocity is constant, there are no acceleration because it is not either accelerating or decelerating.2) An object can have negative initial velocity then accelerate to zero.
2006-11-04 21:15:19 補充：
3) An object can change its direction with constant speed, this will not change the speed but it will change the velocity.
2006-11-04 21:16:04 補充：
So (1),(2),(3) are ALL CORRECT.
2006-11-04 21:15:06 補充：
1) When velocity is constant, there are no acceleration because it is not either accelerating or decelerating.2) An object can have negative initial velocity then accelerate to zero.
2006-11-04 21:15:19 補充：
3) An object can change its direction with constant speed, this will not change the speed but it will change the velocity.
2006-11-04 21:16:04 補充：
So (1),(2),(3) are ALL CORRECT.
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