IIT JEE , AIEEE Forum - Physics , Mechanics - A particle of mass m moves on the X-AXIS AS FOLLOWS: IT STARTS AT t=0 from x=0, and comes

tut_einstein

to rest at time t=1 at the point x=1. No other information is available about its motion during the intermediate time 0<t<1 If $ denotes the instantaneous acceleration of the particle, then:

a) $ cannot remain positive for all t in the time interval 0<t<1

b) |$| can't exceed 2 at any point in its path

c) |$| must be >= 4 at some point in its path

d) $ must change its sign during the motion but no other assertion can be made about with the info give

the answers are (a) and (c)

pls explain how you worked it out.

thanks

ganesha1991

a = v-u/t =-u/t

u = -at

v^2 = u^2 +2as
0 = a^2t^2 + 2as
2as = - a^2t^2
a = - 2s / t^2
t is positive
and s is positive
so a will b e negative for any time
so a in ans

ashish_banga

a is correct
if it starts from rest and comes to rest again, then acceleration at some time would be negative

but how c

ganesha1991

now
I a I = 2s/t^2
this will be obviously more than 2
so
(c) will also be the answer

ganesha1991

@ashish bro
1 correction in ur statement
"then acceleration at some time would be negative"
the correection is
it wud be negative the whole time

apurwa

make a velocity time graph or acc time graph then u will find that
c is also correct
if u still have problem contact me

edison

Its

a) $ cannot remain positive for all t in the time interval 0

Ask & Discuss Questions with Community & Experts