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Homework 1
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1. Walker2 1.P.002.
[349440] A human hair has
a thickness of about 78 µm. (a)
What is
this in meters? (78 mm)(10 -6 m/1 mm)
= 7.8 * 10-5 m (7.8e-5 m) * (1km / 1000 m) =
7.80e-8 km |
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2. Walker2 1.P.014.
[235381] How many
significant figures are there in the following two numbers? (a) 0.0001795 |
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10
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3. Walker2 1.P.021.
[235386] An electronic
advertising sign repeats a message every 23
seconds, day and night, for a week. How many times did the message appear on
the sign in that week? Number =
(1/23sec)*(1week) Number= (1/23
sec) * (1 week)*(7 days/week) * (24 hr/day)*(3600 sec/hr) = 25295.65 Number = 26300
(3 significant figures) |
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4. Walker2 1.P.025.
[235389] What is the speed
in miles per hour of a beam of light traveling at 3.00 v=(3.00e+8 m/s)(3.281
ft/m)(1mi/5280ft)(3600s/1hr)=6.71e+08 mi/hr |
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5. Walker2 1.P.027.
[235391] Suppose 1.1 cubic meter of oil is spilled into the ocean. Find the
area of the resulting slick, assuming that it is one molecule thick, and that
each molecule occupies a cube 0.60 µm on
a side. Volume = 1.1 m3
= Area * height = Area * (0.60e-6 m) Area = 1.1m3
/ (0.60e-6 m) |
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6. Walker2 1.P.029.
[235393] Nerve impulses in
giant axons of the squid can travel with a speed of 20 m/s. (a)
How fast
is this in ft/s? 20 m/s = [20 m/s]*[100
cm/m] *[1in/2.54 cm] * [1ft / 12 in] =65.62 ft/s 65.62 ft/s = (65.62
ft/s)*(1mi/5280 ft) * (3600 s/1hr) = 44.74 |
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7. Walker2 1.P.033.
[235394] New York is
roughly 3000 miles from Seattle. When it is 2:00 p.m. in Seattle, it is 5:00 p.m. in New York. Using this information, estimate the
following. (a)
the
rotational speed of the surface of Earth 3000 miles per 3 hours = 1000 mi/h 3 hours = 1/8 day. Therefore 3000 miles = 1/8 circumference circumference = 8*3000 = 24000 miles circumference = 2 p * radius radius = circumference/(2p) = (24000 miles) / (2 * 3.14159) |
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8. Walker2 1.P.035.
[235396] A Porsche can accelerate
at 11.7 m/s2. (a)
What is
this in ft/s2? acceleration
= (11.7 m/s2) = (11.7 m/s2)(3.281 ft/m) = 38.39 ft/s2
acceleration
= (11.7 m/s2) = (11.7 m/s2)(0.001 km/m)(3600 s/hr)2
= |
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9. Walker2 2.P.003.
[235402] The golfer in
Figure 2-22 sinks the ball in two putts, as shown. Assume that d1
= 11 m and d2 = 2.2 m.
(a)
What is
the distance traveled by the ball? First putt = d1+d2 = 11.0 m + 2.2 m = 13.2 m Total distance = First + Second Putts = 13.2 m + 2.2 m = 15.4m Net change from original position. |
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10. Walker2 2.P.016.
[235409] You jog at 6.2 mi/h for 5.0 mi, then you jump into a car and drive for
another 5.0 mi. With what average speed must you drive if your average speed
for the entire 10.0 miles is to be 10.2 mi/h? average speed = =10.2 mi/hr = v
= (10.0mi) / (t1+t2) |
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11. Walker2 2.P.028.
[235417] A 747 airliner
reaches its takeoff speed of 167 mi/h in
38.9 s. What is the magnitude of its
average acceleration? a = (167 mi/h –
0) / (38.9 s) a = (167 mi/h)*
(1609 m / mi)*(1hr/3600s)/38.9s a = 1.919 m/s2
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12. Walker2 2.P.031.
[235419] A car is
initially traveling due north at 21.0 m/s. (a)
Find the
velocity of the car after 5.50 s if its acceleration is 1.60 m/s2
due north V= v0 + a t = (21.0 m/s) + (1.60m/s2)
(5.50s) = 29.8 m/s V= v0 + a t = (21.0 m/s) - (1.95m/s2)
(5.50s) = 10.3 m/s |
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13. Walker2 2.P.032.
[235420] A motorcycle moves
according to the velocity-versus-time graph shown in Figure 2-28. (The
vertical axis is marked in increments of 4 m/s
and the horizontal axis is marked in increments of 6 s.) Find the average acceleration of the motorcycle
during each of the segments, A, B, and C.
A: acceleration a = (vf-vi)/(tf-ti)
= (8.0 m/s –0) (6.0s – 0) = 1.33 m/s2. [1.33] m/s2
(A) B: acceleration a = (vf-vi)/(tf-ti)
= (8.0 m/s –8.0m/s) (18.0s - 6.0s) = 0 m/s2. C: acceleration a = (vf-vi)/(tf-ti)
= (4.0 m/s –8.0m/s) (30.0s – 18.0s) A = (-4.0m/s) /
(12 s) = -0.33 m/s2. |
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14. Walker2 2.P.039.
[235425] Landing with a
speed of 91.3 m/s, and traveling due south, a jet comes
to rest in 995 m. Assuming the jet slows with
constant acceleration, find the magnitude and direction of its acceleration.
(Include the sign for the magnitude.) v2 =
v02 +2a(x-x0) 0 = (91.3 m/s)2
+ 2 a (995m) a = - (91.3 m/s)2
/ [2 (995m) ] [-4.19] m/s2
(o) due north
(_) due south
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15. Walker2 2.P.049.
[235433] A rocket blasts
off and moves straight upward from the launch pad with constant acceleration.
After 3.4 s the rocket is at a height of 80.0 m. (a)
What is
the acceleration of the rocket? y=y0
+v0 t + a t2 / 2 v =
v0 + a t = 0 + (13.8 m/s 2)(3.4 s) = 47.06 m/s |
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16. Walker2 2.P.079.
[235452] A hot air balloon
is descending at a rate of 1.8 m/s when a passenger drops a camera. (a)
If the
camera is 55 m above the ground when it is dropped,
how long does it take to reach the ground? y =
y0 +v0 t + a t2 /2 |