Ablue train of mass 50 kg moves at 4 m/s toward a green train of 30 kg initially at rest. the trains collide. after the collision the green train moves with a speed of 3 m/s. what is the final momentum of the blue and green train combined?
a. 90 kgm/s
b. 110 kgm/s
c. 50 kgm/s
d. 200 kgm/s

The heater element of a 120 v toaster is a 5.4 m length of nichrome wire, whose diameter is 0.48 mm. the resistivity of nichrome at the operating temperature of the toaster is 1.3 × 10-6 ω·m. the toaster is operated at a voltage of 120 v. (a) what is the power drawn by the toaster? (b) if the cost of electricity is 12 ¢ per kilowatt-hour, and it takes 2 minutes to toast bread, how much does it cost for toasted bread? (c) when the heater element is at room temperature, is the resistivity in the nichrome wire greater than, less than, or equal to it’s resistivity when at operating temperature? explain.