Question

Figure (3-E4) shows the graph of the x-coordinate of a particle going along the X-axis as a function of time. Find (a) the average velocity during 0 to 10 s, (b) instantaneous velocity at 2, 5, 9 and 12s.

Figure

Answer 1

(a) Displacement from t = 0 s to t = 10 s:
x = 100 m
Time = 10 s
Average velocity from 0 to 10 seconds,
$v_{avg}=\frac{x}{t}=\frac{100}{10}=10\mathrm{m}/\mathrm{s}$

(b) Slope of the x–t graph gives the velocity.
At 2.5 s, slope = $\frac{50-0}{2.5-0}=20$.
⇒ v_inst = 20 m/s
At 5 s, v_inst = 0.
At 8 s, v_inst = 20 m/s.
At 12 s, v_inst = −20 m/s.