$A$ body of mass $1\,kg$ is thrown upwards with a velocity $20\,m/s$. It momentarily comes to rest after attaining a height of $18\,m$. How much energy is lost due to air friction? (Given $g = 10\,m/s^2$)

Which of the following statements is $NOT$ true?

$A$ ball is falling freely from a height. When it reaches $10 ~m$ height from the ground,its velocity is $v_0$. It collides with the ground,loses $50 \%$ of its energy,and rises back to a height of $10 ~m$. Then the velocity $v_0$ is (in $~m / s$)

In a perfectly inelastic collision,two spheres made of the same material with masses $15 \ kg$ and $25 \ kg$,moving in opposite directions with speeds of $10 \ m/s$ and $30 \ m/s$,respectively,strike each other and stick together. The rise in temperature (in $^{\circ}C$),if all the heat produced during the collision is retained by these spheres,is: (specific heat of sphere material $31 \ cal/kg \cdot ^{\circ}C$ and $1 \ cal = 4.2 \ J$)

$A$ stationary object of mass $10 \ kg$ is subjected to two mutually perpendicular forces of $4 \ N$ and $3 \ N$. What will be its kinetic energy after $10 \ s$?

Consider two carts,of masses $m$ and $2m$,at rest on an air track. If you push both the carts for $3\,s$ exerting equal force on each,the kinetic energy of the light cart is