phy motion MC

1. car travels on straight road from A to B with uniform acceleration. Its speed v1 at instant when half of journey time from A to B is over, its speed is v2 at the midway of A and B.
A. v1 is always < v2
B. v2 is always
C.v1 always=v2
D. whether v1 isgreater orsmaller than v2 depends on its initial velocity at A
直覺上好明顯係A﹐若果要有步驟的話。我估可以如下
Since the speed is uniform accelerate﹐so at B the speed is max, denoted it by vm
Let the time used is t and the distance is s, acceleration is a
v1 is the speed at instant when half of journey time from A to B
v1=u+at/2=0+at/2=vm/2
v2 is the speed at the midway of A and B.
Since s/2=ut+(1/2)at^2=(1/2)at^2
s=at^2, t=√(s/a)
v2=at=a√(s/a)=√(as)=vm=(√2/2)vm
So v1 is always < v2
The answer is A