Question

A particle travels in a straight line with speed v.

Answer 1

Answer:

D 60°

Explanation:

Using trigonometry:

- The new speed (v/2) of the particle corresponds to the hypothenuse

- The component of v/4 represents the side adjacent  to the angle that we want fo find, $\theta$

So we can write:

$cos \theta = \frac{adjacent}{hypothenuse}=\frac{v/4}{v/2}=\frac{1}{2}$

So we find the angle

$\theta= cos^{-1} (\frac{1}{2})=60^{\circ}$

Answer 2

Answer:

D 60°

Explanation:

Using trigonometry in the attached image:

$cos\alpha =\frac{v/4}{v/2}$

$cos\alpha =\frac{1}{2}$

$\alpha =cos^{-1} \frac{1}{2}$

Angle=60°