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?

As , plants meet their needs for making food from air, soil, water, and the sun's energy in a process called there are plants called grow high in trees without here are words to put in the blanks. 1.) producers 2.) consumers 3.) chloroplasts 4.) epiphytes

Agroup of students is studying convection currents. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other in an area with warm air. after 10 minutes, the balloons are released from a height of 1 meter. which of the following do the students most likely observe? question 2 options: the balloons rise at the same rate. both balloons are the same size. the ballons both rise. the cold ballon is larger than the warm balloon. the cold balloon expands and rises. the warm balloon shrinks and sinks. the warm balloon expands and rises. the cold balloon shrinks and sinks.

Suppose a wheel with a tire mounted on it is rotating at the constant rate of 2.15 times a second. a tack is stuck in the tire at a distance of 0.373 m from the rotation axis. noting that for every rotation the tack travels one circumference (a) find the tack's tangential speed. (b) what is the tacks radial acceleration?