需要前辈打救,

青青狼

A)a plane traveling with an initial speed of 100km/hr accelerates at a rate of 500 km/hr^2 along a straight line.How long will it take to reach a speed 500 km/hr?
also,through what distance does the plane travel during this time?


B)the position of a particle along a straight line is given by sp =1t^3-3t^2+5t
   1)determine magnitude of the velocity and acceleration as a function of time .

    2)compute the magnitude of the velocity and acceleration at t=10 s.


I know my question may seem quite easy,but i can not fix it myself ,considering that cari   has many math students here
plz help me thank you




真的做到不行了   谢谢

^自由的蓝天^

a)
initial speed,u=100km/hr
acceleration,a=500km/hr^2
final speed,v=500km/hr

玩unit：(km/hr) / (km/hr^2)=hr
different in speed/acceleration=time taken
(v-u)/a=t
(500-100)/500=0.8hr= 48min

(这个不太确定）
area under curve

        v(km/hr)
500   1            1
        1           1
        1         1
        1       1
100   11111111111111111
        t(hr)  0       0.8

d={(500-100) x 0.8}/2
d=160km
(这个不太确定）

b)
   s=1t^3-3t^2+5t

i) v=ds   (differentiate of s)
   v=3t^2-6t+5

   a=dv   (differentiate of v)
   a=6t-6

ii)
   t=10s
   v(10)=3(10)^2-6(10)+5
   v(10)=245 (去问要什么unit）

   a(10)=6(10)-6
   a(10)=54 (去问要什么unit）

青青狼

谢谢你，帮了我很大的忙了

青青狼

还有什么建议吗
谢谢