请师兄师姐们指点指点(Tangential and Normal components of acceleration)

Harry7Kewell

希望请师兄师姐们可以帮帮忙做这两题！

Q1.In below problems,the velocity V and acceleration A of a moving object are given at a certain instant.Find tangential and normal components of acceleration at this instant.

V=2i+3j-k,A=-i-5j+2k

Q2.Where on the trajectory of R(t)=(2t^2-5t)i+(5t+2)j+4t^2k is the speed minimized? What is the minimum speed?

[ 本帖最后由 Harry7Kewell 于 21-9-2006 02:49 PM 编辑 ]

Harry7Kewell

没有人会做吗？或是问题出了毛病  ？

R(t)=(2t^2-5t)i+(5t+2)j+4t^2k
Use differentiation to solve the problem. I din try b4 but it wont be too hard.

The first one is easy. just do it by urself

Harry7Kewell

Speed 是不是要deferentiate两次呢?但如果deferentiate两次的话就变成constant了,那如何找minimum呢?

mictiong85

原帖由 Harry7Kewell 于 22-10-2006 08:52 AM 发表
Speed 是不是要deferentiate两次呢?但如果deferentiate两次的话就变成constant了,那如何找minimum呢?

velocity／speed不是differentiate两次，一次就好了。accelaration才是differentiate两次
当然，我说指的是从R(t)开始differentiate

[ 本帖最后由 mictiong85 于 23-10-2006 06:45 PM 编辑 ]

Harry7Kewell

但我要找minimum或maximum是不是要deferentiate两次呢?