A passenger railroad car has a total of 8 wheels. Springs on each wheel compress--slightly--when the car is loaded. Ratings for the car give stiffness per wheel (the spring constant, treating the entire spring assembly as a single spring) as 2.8×10^7N/m. When 30 passengers, each with average mass of 80 kg, board the car, how much does the car move down on its spring suspension?

Explanation:

mg = kx

x = mg/k

x = 30(80)(9.8)/2.8e7 = 0.00084 m  ≈ 1 mm

when jerome paddle in flowing river towards east the net speed of jerome will increase

so the net speed of jerome will be given as

now the speed of paul will be same as it is given as he is running on the ground

so

so here we can say since the speed of jerome is more so he will win the race

now as we know the distance so the time difference is given as

so jerome will reach first and the time difference will be 203.55 s or 3.4 min