;A heavy steel ball of mass greater than 1 kg moving with a speed of 2m/ s collides head on with a stationary ping pong ball of mass less than 0.1 g. The collision is elastic. After the collision the ping pong ball moves approximately with a speed

A ball moving with a velocity v strikes a wall moving toward the ball with a velocity u. An elastic impact lasts for t sec. Then the mean elastic force acting on the ball is ;

একটি বস্তুকে নির্দিষ্ট উচ্চতা থেকে ফেলে দেওয়া হলো। ভূমি হতে 5.0 m উচ্চতায় গতিশক্তি বিভব শক্তির 4 গুণ হলে কত m  উচ্চতা হতে বস্তুটিকে ফেলে দেয়া হয়েছিল?  

A heavy ball moving with speed $v$ collides with a tiny ball. The collision is elastic, then immediately after the impact, the second ball will move with a speed approximately equal to-

A 50 gm ball collides with another ball of mass 150gm, moving in its direction of motion, After collision the two ;balls move at a an angle $30^{0}$ with their initial direction. Ratio of their velocities after collision is