The vector $\overrightarrow { \mathbf { r } }$ indicates the instantaneous displacement of a projectile from the origin.At the instant when the projectile is at $\overrightarrow { \mathbf { r } }$ ,its velocity and acceleration vectors are $\overrightarrow { \mathbf { v } }$ and $\overrightarrow { \mathbf { a } }$ .Which statement is correct?
A) $\overrightarrow { \mathbf { v } }$ is always perpendicular to $\overrightarrow { \mathbf { r } }$ .
B) $\overrightarrow { \mathbf { a } }$ is always perpendicular to $\overrightarrow { \mathbf { r } }$ .
C) $\overrightarrow { \mathbf { a } }$ is always perpendicular to $\overrightarrow { \mathbf { v } }$ .
D) $\overrightarrow { \mathbf { a } }$ is always perpendicular to $\overrightarrow { \mathbf { v } } _ { x }$ .
E) $\overrightarrow { \mathbf { a } }$ is always perpendicular to $\overrightarrow { \mathbf { v } } _ { y }$ .

Question

Quizplus · Accepted Answer

$\overrightarrow { \mathbf { a } }$ is always perpendicular to $\overrightarrow { \mathbf { v } } _ { x }$ because the acceleration of a projectile is always in the vertical direction, and the velocity of a projectile has both horizontal and vertical components.

The Vector r→\overrightarrow { \mathbf { r } }r Indicates the Instantaneous Displacement of a Projectile from the Origin

The Vector $\overrightarrow { \mathbf { r } }$ Indicates the Instantaneous Displacement of a Projectile from the Origin