🛠️ JEE🧲 Physics

If \(\vec{L}\) and \(\vec{P}\) represent the angular momentum and linear momentum respectively of a particle of mass ' \…

Q1 FREE PREVIEW

If \(\vec{L}\) and \(\vec{P}\) represent the angular momentum and linear momentum respectively of a particle of mass ' \(m\) ' having position vector \(\vec{r}=\mathrm{a}(\overset{^}{\mathrm{i}}\cos \omega \mathrm{t}+\overset{^}{\mathrm{j}}\sin \omega \mathrm{t})\). The direction of force is:

a

Opposite to the direction of \(\vec{r}\)

b

Opposite to the direction of \(\vec{L}\)

c

Opposite to the direction of \(\vec{P}\)

d

Opposite to the direction of \(\vec{L}\times \vec{P}\)

✓ Correct answer: a)

Opposite to the direction of \(\vec{r}\)

Explanation

Given position vector of particle in circular motion.
\(\vec{r}=a\cos \omega t\overset{^}{i}+a\sin \omega t\overset{^}{j}\)
Velocity is time derivative of position.
\(\vec{v}=\frac{d\vec{r}}{\mathrm{dt}}=−a\omega \sin \omega t\overset{^}{i}+a\omega \cos \omega t\overset{^}{j}\)
Acceleration is time derivative of velocity.
\(\vec{a}=\frac{d\vec{v}}{\mathrm{dt}}=−a{\omega }^{2}\cos \omega t\overset{^}{i}−a{\omega }^{2}\sin \omega t\overset{^}{j}\)
Force is proportional to acceleration.
\(\vec{F}=m\vec{a}\)
Acceleration vector is opposite in direction to position vector.
Therefore acceleration is antiparallel to position vector.

Practice more JEE Physics PYQs

See every question on Rotational Motion, or browse the full JEE question bank.

See all questions on Rotational Motion →