Question

A particle starts moving in xy – plane at 2 m/s along x – axis. 2 second later, its velocity is 4 m/s in a direction making 60⁰ with positive x – axis. Its average acceleration for this period of motion is:

• A. $\sqrt { 5 }$ m/s², along y – axis
• B. $\sqrt { 3 }$ m/s², along y – axis
• C. $\sqrt { 5 }$ m/s², at 60⁰ with positive x – axis
• D. 3 m/s², at 60⁰ with positive x – axis

Answer 1

Answer: (B)

$\sqrt { 3 }$ m/s², along y – axis

Answer 2

$\vec { a } = \frac { \vec { V } _ { f } - \vec { V } _ { i } } { \Delta t }$

= $\frac { [ 4 \cos 60 \hat { i } + 4 \sin 60 \hat { j } ] - [ 2 \hat { i } ] } { 2 }$ = $\frac { ( 2 \hat { \mathrm { i } } + 2 \sqrt { 3 } \hat { \mathrm { j } } ) - 2 \hat { \mathrm { i } } } { 2 }$ = $\sqrt { 3 } \hat { j }$

m/s²