James Stewart-Calculus_ Early Transcendentals-Cengage Learning (2015)

878 Chapter 13 Vector Functions
1. The table gives coordinates of a particle moving through
space along a smooth curve.
(a) Find the average velocities over the time intervals
[0, 1], [0.5, 1], [1, 2], and [1, 1.5].
(b) Estimate the velocity and speed of the particle at t − 1.
t x y z
0 2.7 9.8 3.7
0.5 3.5 7.2 3.3
1.0 4.5 6.0 3.0
1.5 5.9 6.4 2.8
2.0 7.3 7.8 2.7
2. The figure shows the path of a particle that moves with
position vector rstd at time t.
(a) Draw a vector that represents the average velocity of
the particle over the time interval 2 < t < 2.4.
(b) Draw a vector that represents the average velocity over
the time interval 1.5 < t < 2.
(c) Write an expression for the velocity vector vs2d.
(d) Draw an approximation to the vector vs2d and estimate
the speed of the particle at t − 2.
y
2
1
r(2.4)
0 1 2
r(2)
r(1.5)
3–8 Find the velocity, acceleration, and speed of a particle with
the given position function. Sketch the path of the particle and
draw the velocity and acceleration vectors for the specified value
of t.
3. rstd − k2 1 2 t 2 , tl, t − 2
4. rstd − kt 2 , 1yt 2 l, t − 1
5. rstd − 3 cos t i 1 2 sin t j, t − y3
6. rstd − e t i 1 e 2t j, t − 0
7. rstd − t i 1 t 2 j 1 2 k, t − 1
8. rstd − t i 1 2 cos t j 1 sin t k, t − 0
9–14 Find the velocity, acceleration, and speed of a particle with
the given position function.
9. rstd − kt 2 1 t, t 2 2 t, t 3 l
10. rstd − k2 cos t, 3t, 2 sin t l
x
11. rstd − s2 t i 1 e t j 1 e 2t k
12. rstd − t 2 i 1 2t j 1 ln t k
13. rstd − e t scos t i 1 sin t j 1 t kd
14. rstd − kt 2 , sin t 2 t cos t, cos t 1 t sin tl , t > 0
15–16 Find the velocity and position vectors of a particle that has
the given acceleration and the given initial velocity and position.
15. astd − 2 i 1 2t k, vs0d − 3 i 2 j, rs0d − j 1 k
16. astd − sin t i 1 2 cos t j 1 6t k,
vs0d − 2k, rs0d − j 2 4 k
17–18
(a) Find the position vector of a particle that has the given
acceler ation and the specified initial velocity and position.
; (b) Use a computer to graph the path of the particle.
17. astd − 2t i 1 sin t j 1 cos 2t k, vs0d − i, rs0d − j
18. astd − t i 1 e t j 1 e 2t k, vs0d − k, rs0d − j 1 k
19. The position function of a particle is given by
rstd − kt 2 , 5t, t 2 2 16tl . When is the speed a minimum?
20. What force is required so that a particle of mass m has the
position function rstd − t 3 i 1 t 2 j 1 t 3 k?
21. A force with magnitude 20 N acts directly upward from the
xy-plane on an object with mass 4 kg. The object starts at the
origin with initial velocity vs0d − i 2 j. Find its position
function and its speed at time t.
22. Show that if a particle moves with constant speed, then the
velocity and acceleration vectors are orthogonal.
23. A projectile is fired with an initial speed of 200 mys and
angle of elevation 60°. Find (a) the range of the projectile,
(b) the maximum height reached, and (c) the speed at impact.
24. Rework Exercise 23 if the projectile is fired from a position
100 m above the ground.
25. A ball is thrown at an angle of 45° to the ground. If the ball
lands 90 m away, what was the initial speed of the ball?
26. A projectile is fired from a tank with initial speed 400 mys.
Find two angles of elevation that can be used to hit a target
3000 m away.
27. A rifle is fired with angle of elevation 36°. What is the muzzle
speed if the maximum height of the bullet is 1600 ft?
28. A batter hits a baseball 3 ft above the ground toward the
center field fence, which is 10 ft high and 400 ft from home
plate. The ball leaves the bat with speed 115 ftys at an
angle 508 above the horizontal. Is it a home run? (In other
words, does the ball clear the fence?)
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