Question

If a body moves for 2 s with 15 m/s velocity towards east and then moves with 5 m/s velocity for 8 s towards north, then average velocity is :

• A. 5 m/s
• B. 15 m/s
• C. 30 m/s
• D. 7.5 m/s

Answer 1

The Correct Option is A

Key Idea: $ \text{Average}\,\text{velocity}\,\text{=}\,\frac{\text{Displacement}}{\text{Time}\,\text{taken}} $
Let body move along AB, then BC.
Distance travelled in 2s.
$ {{\text{S}}_{1}}=15\times 2=30\,m $
Distance travelled in 8s
$ {{S}_{2}}=5\times 8=40\,m $
$ \therefore $ Displacement $ AC=\sqrt{{{(30)}^{2}}+{{(40)}^{2}}} $
$ =\sqrt{900+1600}=\sqrt{2500} $
$ =50\,m $
Hence average velocity
$ =\frac{\text{displacement}}{\text{time}\,\text{taken}} $
$ =\frac{50}{8+2}=\,5\,m/s $