Homework Help: physics

Posted by parul on Monday, May 28, 2012 at 2:28am.

a car traveled at uniform velocity of 20m/sec for 5 sec the brakes are applied and car retards uniformly and come to rest in further 8 sec.find
a)distance traveled in first five sec
b)distance traveled after breaks are applied
c)total displacement during this period and its avrage velocity in whole journy.

physics - Elena, Monday, May 28, 2012 at 8:37am
(a) s1 =v•t =20•5 =100 m,
(b)
v(final) =v - a•t
v(final) =0
a =v/t,
s =v•t - at²/2 =
= v•t - v•t²/2•t =v•t/2=20•8/2=80 m
(c)
s =s1+s2 = 100+80 = 180 m
(d)
v(ave) = s/t =180/(8+5) = 13.85 m/s.

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