

\(u_0=\sqrt{2gh}\)
\(v_z = \sqrt{2g(3h)}\)
\(tan\theta=\frac{v_z}{u}=\sqrt3\)
\(\theta=60^{\circ}\)
\(d=u_0T=u_0\sqrt{2(\frac{3h}{g})}=\sqrt{2gh}\sqrt{2(\frac{3h}{g})}\)
Velocity after the collision,
\(v_1=ev_z=\sqrt{2gh}\)
\(\vec{v}=v_1\hat{k}+u_0\hat{i}\)
\(=\sqrt{2gh}[\hat{i}+\hat{j}]\)
\(h_1=\frac{v_1^2}{2g}=h\)
Finally, \(u_0=\sqrt{2gh},\theta=60^{\circ},\frac{d}{h}=2\sqrt{3}\)
The center of a disk of radius $ r $ and mass $ m $ is attached to a spring of spring constant $ k $, inside a ring of radius $ R>r $ as shown in the figure. The other end of the spring is attached on the periphery of the ring. Both the ring and the disk are in the same vertical plane. The disk can only roll along the inside periphery of the ring, without slipping. The spring can only be stretched or compressed along the periphery of the ring, following Hookeβs law. In equilibrium, the disk is at the bottom of the ring. Assuming small displacement of the disc, the time period of oscillation of center of mass of the disk is written as $ T = \frac{2\pi}{\omega} $. The correct expression for $ \omega $ is ( $ g $ is the acceleration due to gravity): 
Let $ a_0, a_1, ..., a_{23} $ be real numbers such that $$ \left(1 + \frac{2}{5}x \right)^{23} = \sum_{i=0}^{23} a_i x^i $$ for every real number $ x $. Let $ a_r $ be the largest among the numbers $ a_j $ for $ 0 \leq j \leq 23 $. Then the value of $ r $ is ________.
Friction is defined as the resistance offered by the surfaces that are in contact when they move past each other.
There are four categories of Friction- static friction, sliding friction, rolling friction, and fluid friction.
In Sliding Friction, the weight of the sliding object calculates the amount of sliding friction present between the two objects. The sliding friction is supposed to be greater as the pressure exerted by the heavy object on the surface it slides over is comparably more.
Friction between a circular object and the surface is called as Rolling Friction. It is required to overcome sliding friction is more than the force required to overcome the rolling friction.
Friction that keeps an object at rest without initiating any relative motion between the body and the surface is termed as Static Friction. For example, a parked car resting on the hill, a hanging towel on the rack. The maximum force of static friction is directly proportional to the normal force.
Fluid Friction is the kind of friction that is exerted by the fluid on the object that is moving through a fluid.