in a high-energy collision of a primary cosmic-ray particle near the top of the Earth’s atmosphere, 120 km above sea level, a proper is created with a total energy of 135 GeV, traveling vertically downward. In its proper frame this poin decays 35.0 ns after its creation. At what altitude above sea level does the decay occur? The rest energy of a pion is 139.6 MeV.

Three identical balls are placed on a frictionless horizontal surface touching each other. They stick to each other because of adhesive. Another ball of same radius and mass m is placed over the void created by the three balls. Find the forces applied by the balls kept on the floor to each other if the system remains in equilibrium.

A car loaded with water having total mass 1000 kg moves on a straight horizontal Road starting from rest under the action of a force of 100 Newton. The water spills throw a small hole in the bottom at a rate of 0.1 KG per second the velocity of cart after 300 seconds is nearly.

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