Two friends are travelling downstream on a raft drifting along with the same speed as the river. At = 0, Friend-1 jumps off the raft and start swimming downstream. At = 30 m, Friend-1 turns around and starts swimming upstream until he reaches the raft. By this time the raft has drifted 2 m downstream. Friend-1 swims at a constant speed relative to the river. a) Find the speed of the river. b) How does your answer to part a) depend on the Friend-1’s speed relative to the river?

1. consider the case in which air fills air shocks on a truck trailer. the pressure in the shocks is 2 mpa. the temperature is 300 k. the diameter of the shock piston is 10 cm and the initial length of the cylindrical cavity containing the compressed air is 40 cm. a. the truck is gradually loaded over a period of a day in a static setting. the temperature is held constant for the atmosphere and thus for the gas shock. calculate the compressibility of the air in the shock for this condition when the truck is initially being loaded. b. if the shocks were loaded in a dynamic setting by driving over bumps, what would be the compressibility? state your assumption. c. what is the initial load on the shock if the shock is in an atmospheric 100 kpa? d. if the shock is compressed using the process described in part a, and the air shock compressed air cavity length decreases to 20 cm, what is the additional load applied to the shock?

Which of these is constant for all types of electromagnetic radiation in a vacuum? select one: a. wavelength b. frequency c. photon energy d. amplitude e. velocity

Failure to accomplish erikson’s psychosocial task of late adulthood leads to despair. a. true b. false