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course phy 201
Aaron GobblePhysics homework on 9/20 notes
Ch 2 problems
1. What must avg speed be to travel 235km in 3.25 hours?
235km / 3.25hr= 72.3km/h
2. A bird can fly 25km/h. How long does it take to fly 15km?
15km / 25km/h= 0.6hr
3. Traveling 110km/h. How far in 2seconds?
110km/h / .000555hr= 0.061km
4. Convert 35mi/h
35mi/h=
56.3km/h
15.6m/s
51.3ft/s
5. A ball moves from 3.4cm to –4.2cm during time 3.0s to 6.1s. Average velocity?
(-4.2s-3.4s) / (6.1s-3.0s)= -2.45cm/s
6. Particle at –2.0s and –4.2cm, then 4.5s and 8.5cm. What is average velocity?
(8.5cm+4.2cm) / (4.5s+2.0s)= 1.95cm/s
9. Person jogs eight laps around quarter mile track in 12.5min. Calculate average speed and average velocity.
Average speed= 0.16mi/min
Average velocity= 0 mi/min because there was no net change in displacement.
10. Two trains approach each other. Both have a speed of 95km/h. If they are 8.5km apart how long before they reach each other?
4.25km / 95km/h= 0.045h
16. Car accelerates from rest to 95km/h in 6.2s. What is average acceleration in m/s2?
1583m/s / 6.2s= 255m/s2
22. Car slows from 23m/s to rest in 85m. What was its acceleration?
VF2=Vo2+2adx
0= (23m/s)2+2a(85m)
(-23m/s)2=2a(85m)
529m2/s2=2a(85m)
6.22m/s2=2a
a= 3.11m/s2
27. Car traveling 85km/h stops in .80 m. What’s avg accel?
Vo2=vf2*2adx
-557.4321m/s=2a(.80m)
696.79=2a
a=-348.4m/s2= -35.5g’s
34. Car free falls, how long until 85km/h? 8.67s
9.80m/s2(T)=85m/s
T=8.67sec
37. Ballplayer catches ball after throwing straight up after 3.0s. vF? What height did it reach?
Dx=.5(9.8m/s2)(1.5s)2
Dx= 11m
Vf2=2(9.8m/s2)(11m)
Vf=14.7m/s
52. Car avg acceleration in 2nd and 4th gear? 1.35m/s2. Distance in fouth gear?
43m/s=(36m/s)^2+2(.7m/s2)(dx)
dx= 395m
58. Accel on moon 1/6 of that on earth. If object thrown up on moon how many times higher will it go? 6x
you need to show this
63. 95m long train. Begins from rest, passes guy 180m away at 25m/s. How fast will the end of the train be going by him?
(25m/s)2=2a(180m)
a= 6.94m/s2
vf2= 2(6.94m/s2)(275m)
vf= 61.8m/s
Right reasoning, but your arithmetic appears to be off.
&#This looks good. Let me know if you have any questions. &#
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