`v=v_(0)+lambdax`
`(dv)/(dt)=0+lambda(dx)/(dt)=lambdav`
`a=lambdav`
At `x=0, v=v_(0)`
`a=lambdav`
`(dv)/(dt)=lambdav`
`int_(v_(0))^(v)(dv)/v=lambda int_(0)^(t) dt`
`|log_(e)v|_(v_(0))^(v)=lambda|t|_(0)^(t)`
`log_(e)v-log_(e)v_(0)=lambdat`
`log_(e)(v/v_(0))=lambdat`
`v/v_(0)=e^(lambdat)`
`v=v_(0)e^(lambdat)`