Question

A particle is projected with velocity u at angle $\theta$ with horizontal at $t = 0.$ What is the magnitude of change in the velocity of the particle when it is at maximum height?

• A. $\frac{u\, cos\, \theta}{2}$
• B. u cos $\theta$
• C. u sin $\theta$
• D. none of these

Answer 1

Answer: (C)

$\vec{u} _{i}=u\, cos \,\theta \hat{i}+u\, sin \,\theta \hat{j}$
$\vec{u}_{f}=u\, cos \,\theta \hat{i} $
$ \Delta\vec{u}=\vec{u}_{f}-\vec{u}_{i}=-u\, sin \,\theta \hat{j} $
$\left|\Delta\vec{u}\right|=u\, sin \,\theta$