A body $A$ $$ , of mass $m=0.1\mathrm{k}\mathrm{g}$ $$ has an initial velocity of $3\hat{i}{\mathrm{m}\mathrm{s}}^{-1}$ $\stackrel{}{}{}^{}$ . It collides elastically with another body, $B$ $$ of the same mass which has an initial velocity of $5\hat{j}{\mathrm{m}\mathrm{s}}^{-1}$ $\stackrel{}{}{}^{}$ . After collision, A moves with a velocity $\stackrel{?}{v}=4(\hat{i}+\hat{j})$ $\stackrel{}{}\stackrel{}{}\stackrel{}{}$ . The energy of $$ $B$ after collision is written as $\frac{}{}$ $\frac{x}{10}\mathrm{J}$ . The value of $x$ $$ is

Vertical component of velocity just after collision $=\frac{u}{2\sqrt[]{2}}$

$k_i=\frac{m{u}^2}{2}{k}_f=\frac{1}{2}m\frac{u^2}{2}+\frac{1}{2}m\frac{u^2}{8}=\frac{5m{u}^2}{16}$ $\frac{}{\text{exception 25:}}$

Fraction  $=\frac{k_i-k_f}{k_i}=1-\frac{\frac{5m{u}^2}{16}}{\frac{m{u}^2}{2}}=1-\frac{5}{8}=\frac{3}{8}$

Using Conservation of Mechanical Energy at point-A and at point-B, we can write
K_B = U_A - U_B [Since K_A = 0]
⇒ (1/2)mv_B² = mg (h_A - h_B)
⇒ v_B = √ (2 × 10 × (10 - 5) = 10m/s

No. Since kinetic energy is a scalar quantity, it only depends on speed of the body and not the direction. So if the direction of the body is changed but the speed remains unchanged, there won't be any effect on the kinetic energy. However, if changing the direction also changes the speed of the bod

If you look closely at the formula of kinetic energy (1/2*m*v^2), the velocity is squared which automatically gives a positive integer. And mass of the body can never be a negative value, which leads to the result being a positive integer.

The 1/2 is a result of mathematical calculation, which occurs when we integrate? vdv in the formula of work done according to Newton's second law of motion. Without this, the final result will turn out to be twice of the actual value.