A level

题目

A level
A particle of mass 2kg is acted upon by a horizontal force of magnitude 10N for 8 seconds,in which time time it moves from rest until it is travelling with speed v米每秒.Show that v=40.The particle continues to move with this speed for the next 10 seconds.It is then brought to rest by the application of a constant resisting force of magnitude x newtons.The total distance travelled is 800m.Find the time for which the particle is decelerating,and the value of X

答案

v1-v0=at,so,a=40/8=5(m*s^-2)s1=v0*t+1/2*at^2=0.5*5*64=160ms2=vt=40*10=400mso,s3=800-400-160=240mBecause the particle is acted by a constant force:v1^2-v0^2=2as so,a2=-64/(2*240)=-0.133(m*s^-2)so t=8/0...