HP HP-20S - Page 105

Example 1: A ball is thrown straight up at an initial velocity of 20
meters per second from a height of 2 meters. Ignoring air resistance,
when will it reach the ground? The acceleration due to gravity is ap-
proximately 9.81 meters per second?.
According to Newtonian mechanics, this problem may be expressed
as the second degree polynomial f(f) = —1/,(9.81)#> + 20t + 2,
where t is time in seconds. When the ball hits the ground, f(t) = 0.
Keys:
(52) (PRGM] (] [LOAD]
E
() (PREM]
9.81 (3] 2 {4
[XEQ) A
20 [XEQ] B
2 [XEQ] C
[Xeq) D
R/S
Display:
qUAd
00-
—2_
—4.9050
20.0000
2.0000
4.1751
—0.0977
Description:
Loads program.
Exits Program mode.
Enters a.
Enters b.
Enters c.
Calculates ¢;.
Calculates t,.
Since a negative time has no meaning in the context of this problem,
the first result, 4.1751 seconds, is the meaningful answer.
Example 2: Find the roots of 3x2 + 5x + 3 = 0.
Keys:
3 [xEQ] A
5 [XxEQ] B
3 (xeEQ] C
Display:
3.0000
5.0000
3.0000
Description:
Enters a.
Enters b.
Enters c.
7: Built-in Program Library 103