普物作業題目
20.(a)If the position of a particle is given by x=20t-5t^3,
where x is in meters and t is in seconds,when ,if ever,
is the particle's velocity zero?
(b)When is its acceleration a zero?
(c)For what time range(positive or negative) is a negative?
(d)Positive?
(e)Graph x(t),v(t) and a(t).
22.The position of a particle moving along the x axis depends
on the time according to the equation x=ct^2-bt^3,where x
is in meters and t in seconds.What are the units of
(a)constant c and
(b)constant b ? Let their numerical values be 4.0 and 2.0,
respectively.
(c)At what time does the particle reach its maximum positive
x position? From t=0.0s to t=4.0s,
(d)what distance does the particle move and
(e)what is its displacement?
Find its velocity at times
(f)1.0s
(g)2.0s
(h)3.0s,and
(i)4.0s
Find its acceleration at times
(j)1.0s
(k)2.0s
(l)3.0s,and
(m)4.0s
23.An electron with an initial velocity v0 =1.50*10^5 m/s enters
a region of length L=1.00 cm where it is electrically accelerated
(Fig.2-23). It emerges with v=5.70*10^6 m/s. What is its acceleration,
assumed constant?
100.A parachutist bails out and freely falls 60 m. Then the parachute
opens, and thereafter she decelerates at 2.0 m/s^2. She reaches
the ground with a speed of 3.0 m/s.
(a)How long is the parachutist in the air?
(b)At what height does the fall begin?
應該是這幾題...有錯的話幫我改吧，打完眼花不想校對XD
(應該是第二章沒錯吧，一直怕寫錯)
23題的圖(亂畫的XD)
Nonaccelerating Accelerating
region region
| |
| |
|<----L----->|
| |
| |
| |
| |
------------------------->----------------->
| |
Path of | |
electron | |
| |
| |
| |
| |
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