Acar approaches a train-crossing bell at speed v. the bell has a perceived frequency f1. after the car passes the bell, the driver hears a frequency f2. the two frequencies are in the ratio of 7: 6 (or 6: 7, depending on how you order them).
(a) which frequency will be higher, f1 or f2?
(b) if the speed of sound is 340 m/s, what is the car speed v?

According to newton's second law, when the same force is applied to two objects of different masses, a the object with greater mass will experience a great acceleration, and the object with less mass will experience an even greater acceleration, b. the object with greater mass will experience a smaller acceleration, and the object with less mass will experience a greater acceleration, c. the object with greater mass will experience a greater acceleration, and the object with less mass will experience a smaller acceleration, d. the object with greater mass will experience a small acceleration, and the object with less mass will experience an even smaller acceleration.

Waves that cause the most damage during an earthquake are a. surface waves c. s waves b. p waves d. ocean waves

Consider a 1000 w iron whose base plate is made of 0.5 cm thick aluminum alloy 2024-t6 (ρ = 2770 kg/m3 and cp = 875 j/kg°c). the base plate has a surface area of 0.03 m2. initially, the iron is in thermal equilibrium with the ambient air at 22°c. assuming 90% of the heat generated in the resistance wires is transferred to the plate, determine the minimum time needed for the plate temperature to reach 200°c.