An object starts from rest at x = 0 m and moves with a constant acceleration of 1.6 m/s² along the x-axis. During its journey from x = 12.8 m to x = 20.0 m, its average velocity will be __________.

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RRB ALP Fitter 23 Jan 2019 Official Paper (Shift 3)

Answer 1

Concept:

Equation of motion:

Equations of motion of kinematics describe the basic concept of the motion of an object such as the position, velocity, or acceleration of an object at various times.
These three equations of motion govern the motion of an object in 1D, 2D, and 3D.
Three equations: v = u + at, s = ut + 0.5 at², 2as = v² - u²
Here, u = initial velocity, v = final velocity, s = displacement, t = time
Under the influence of gravity, acceleration a is replaced by acceleration due to gravity g.

Calculation:

Given,

Initial velocity, u = 0 m/s, Acceleration, a = 1.6 m/s²

From the second equation of motion,

s = ut +0.5 at²

12.8 = 0.8 t₁²

\(t_1^2=\frac{12.8}{0.8}=16\)

t₁ = 4 sec.

For s = 20

20 = 0 × t₂ + 0.5 × 1.6 t₂2

t₂ = 5 sec.

The average velocity can be calculated as,

\(v_{avg}=\frac{total\, \, displacement}{total\, \, time\, duration}\)

\(v_{avg}=\frac{20 - 12.8}{5 - 4}=7.2m/s\)

Hence, What is its average velocity 7.2m/s.

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