(13) The velocity of the transverse waves produced by an earthquake is 6.62 km/s

Question

(13) The velocity of the transverse waves produced
by an earthquake is 6.62 km/s, while that of
the longitudinal waves is 12.1146 km/s. A seismograph records the arrival of the transverse waves 67.3 seconds after the longitudonal waves. How far was the earthquake (in units of km)?

A car is moving at a constant speed of 14 m/s when the driver presses down on the gas pedal and accelerates for 11 s with an acceleration of 2 m/s2. What is the average speed of the car during the period? Answer in units of m/s

Explanation / Answer

13)

time diff = time tranverse- time long

67.3 = d/6.62 - d/12.1146

d=982.3 km

14) v average = displacement/time

displacement = v0 t + 1/2 a t^2 = 14*11 + 0.5*2*11^2

v average = (14*11 + 0.5*2*11^2)/11 = 14 + 0.5*2*11 = 25 m/s

15)

so to average 65 mph, find total time

t = d/v = 74/64

total time = time first half + time second half

74/64 = 37/48 + 37/v

v=96 mph

21)

a = dv/dt = (-5.84-7.72)/0.011=-1233 m/s^2

22)

y = y0 + v0y t + 1/2 a t^2

0 = h - 9.4*4.5 -0.5*9.81*4.5^2

h=141.6 m

23)

v^2 = v0^2 + 2 a x

0 = 66^2 +2*a*79

a=-27.57 m/s^2

24)

v = v0 + at

t = -v0/a = 66/27.57= 2.39 s

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