P. 4029. A 2 kg body, moving on a frictionless horizontal track, reaches another object of 3 kg made of the same material, moving in front of the 2-kg object, and collides with it totally inelastically. Their common speed after the collision is 4 m/s. Due to the collision the temperature of the two objects, which was initially the same, is increased, though only by 0.006 oC. The specific heat capacities of the two objects are the same: .
a) What were the initial speeds of the colliding objects before the collision?
b) What percent of the initial kinetic energy is transferred to increase of the internal energy of the two objects?
P. 4030. A house, situated 100 m to the South of a straight road running East--West, contains a television set which is receiving signals from a distant transmitter, also situated South of the road, operating at a frequency of 60 MHz. A bus, travelling along the road in a westerly direction, causes the received signal to fluctuate in intensity, the rate of fluctuation is 2 Hz when the bus is opposite the house and (temporarily) reduces to zero when it is 200 m further along the road. Find the speed of the bus and the direction of the transmitter.
P. 4031. A positron of speed , collides with an electron which was initially at rest, and they annihilate. One of the created photon travels perpendicularly to the original direction of the velocity of the positron.
a) In what direction is the other photon emitted?
b) What is the ratio of the energies of the two photons?