Question

plz explain in detail

Answer 1

v = dx/dt = 2at - 3bt^2
a = dv/dt = 2a -6bt
2a -6bt = 0
t = 2a/6b = a/3b...

Answer 2

Hola!

Given : x = at² - bt³ 

Acceleration is change in velocity per unit time [ a = dv/dt ].

also,
Velocity is change in displacement per unit time [ v = dx/dt ].

Thus,
Acceleration = d²x/dt²

now,
differentiate x = at² - bt³ with respect to t.

dx/dt = 2at - 3bt²

again,

d²x/dt² = 2a - 6bt

acc. to above we know, A. = d²x/dt²

Acceleration = 2a - 6bt

but, ATQ

2a - 6bt = 0

6bt = 2a

t = a/3b

Hence, Time ( t ) = a / 3b

Option [ 3 ] : a/3b is CORRECT ! ! !


Hope it helps! :D