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  1. A particle moving along x-axis has acceleration f, at time t, given by f = f0(1 - (t/T)) , where f0 and T are constants. The particle at t = 0 has zero velocity. In the time interval between t = 0 and the instant when f = 0, the particle’s velocity (vx) is
    1. 1/2 f0
    2. f0
    3. 1/2 f0T
    4. f0T.
Correct Option: C

Here, ƒ = ƒ0 1 -
t
or,
dv
= ƒ0 1 -
t
TdtT

or, dv = ƒ0 1 -
t
dt
T

∴ v = ∫ dv = ∫ ƒ0 1 -
t
dt
T

or v = ƒ0 t -
+ C
2T

where C is the constant of integration.
At t = 0, v = 0.
∴ 0 = ƒ0 0 -
0
+ C ⇒ C = 0
2T

∴ v = ƒ0 t -
2T

if ƒ = 0, then
0 = ƒ0 t -
⇒ t = T
2T

Hence, particle's velocity in the time interval t = 0 and t = T is given by
vx = t = Tt = 0 dv = Tt = 0 ƒ0 1 -
t
dt
T

= ƒ0 t -
T
2T0

= ƒ0 T -
= ƒ0 T -
T
=
1
ƒ0T
2T22



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