help with physics hw?

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cleveland

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1. Vivian is walking to the hairdresser's at 1.3 m/s when she glances at her watch and realizes that she is going to be late for appointment. Vivian gradually quickens her her pace at a rate of 0.090 m/s to the second power . a) what is vivian's speed after 10.0 s? b) at this speed , is vivian walking , jogging, or running very fast?



2. A torpedo fired from a submerged submarine is propelled through the water with a speed of 20.00 m/s and explodes upon impact with a target 2000.0 m away. if the sound of the impact is heatrd 101.4 s after the torpedo was fired, what is the speed of sound in water? (because the ttorpedo is held at a constant speed by its propeller, the effect of water resistance can be neglected.)
 
1)

V = V0 + a*t

V = 1.3 + 0.090*10.0


2)

The time for the torpedo to reach the target is t1 = d/V. The time for sound to return is t2 = d/Vs. The total time is t1 + t2

t1 + t2 = d/V + d/Vs

101.5 = 2000.0*(1/20.00 + 1/Vs)

solve for Vs
 
1) vf = vo + at
vf = 1.3 + 0.90*10
vf = 10.3 m/s

2) Split the times into t1 and t2, where t1 denotes the time before the heard impact and t2 the time of the torpedo after being fired

t1 + t2 = 101.4
d/vo + d/vf = 101.4
2000(1/20 + 1/vf) = 101.4
1/vf = 101.4/2000 - 1/20
1/vf = 0.0007
vf = 1428.57 m/s
 
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