As per given figure, a weightless pulley $P$ is attached on a double inclined frictionless surface. The tension in the string (massless) will be (if $g=10 \mathrm{m} {\mathrm{s}}^{-2}$)

A spherical body of mass $2 \mathrm{kg}$ starting from rest acquires a kinetic energy of $10000 \mathrm{J}$ at the end of $5^{\text{th }}$ second. The force acted on the body is _____ $\mathrm{N}$.

Consider a block kept on an inclined plane (inclined at $45°$) as shown in the figure. If the force required to just push it up the incline is $2$ times the force required to just prevent it from sliding down, the coefficient of friction between the block and inclined plane $(\mu )$ is equal to :

.