acceleration=chane of velocity?

Ok.

1)
velocity is the rate of change of displacement, i.e. the change of displacement per unit time. The instantaneous velocity is given by ds/dt - the first time-derivative of the displacement

In the s-t graph, the instantaneous velocity at time = t is actually given by the tangential slope at time =t.

2)
acceleration is the rate of change of velocity, i.e. the change of velocity per unit time. The instantaneous acceleration is given by dv/dt - the first time-derivative of the velocity.

Hence, the acceleration is also the second derivative of the displacement with respect to time.

In the v-t graph, the instantaneous acceleration at time = t is actually given by the tangential slope at time =t.

3) If your amath teacher is talking about change of displacement per unit time, he/she is correct. (每單位時間的位移變更 = 位移變更率)

4) One more thing to mention: displacement, velocity and acceleration are vectors.

2007-02-18 21:14:42 補充：
解答你的問題:1) Wrong. E.g. a car is moving to right and decelerating--- velocity(right-direction); acceleration(left-direction)2) Wrong. Acceleration is the RATE of change of velocity. 3) Correct only if the Q is talking about instantaneous displacement and instantaneous acceleration.

2007-02-18 21:14:58 補充：
This question 出得唔好。But since 1) and 2) must be wrong, the ans must be (3) onlyHope I can help. Happy new year

正確黎講~
v係rate of change of displacement~
即係change of displacement/change in time
係x-t graph 既slope~
change of displacement=dx
change in time=dt
v=dx/dt
a係rate of change od velocity
係v-t graph既slope
a=dv/dt

我地平時既dy/dx其實係搵緊y-x graph既slope~
differenciation既好處係可以搵番不同點既速度/加速率~
因為如果條graph唔係直線,我地就一定要用differenciation~