Transcript Sects. 6.5 through 6.9

Chapter 6 – part C
Power
Exercise 6.36
36.
A skier of mass 70.0 kg is pulled
up a slope by a motor-driven cable.
(a) How much work is required to pull the
skier a distance of 60.0 m up a 30.0°
slope (assumed frictionless) at a constant
speed of 2.00 m/s?
(b) A motor of what power is required to
perform this task?
Exercise 6.55
55.
The ball launcher in a classic
pinball machine has a spring that has a
force constant of 1.20 N/cm. The surface
on which the ball moves is inclined 10.0°
with respect to the horizontal. The spring
is initially compressed 5.00 cm. Find the
launching speed of a 100-g ball when the
plunger is released. Friction and the
mass of the plunger are negligible.
Exercise 6.52
52.
A particle is attached between
two identical springs on a horizontal
frictionless table. Both springs have
spring constant k and are initially
unstressed. (a) The particle is pulled a
distance x along a direction
perpendicular to the initial configuration
of the springs. Show that the force
exerted by the springs on the particle is


ˆ (b) Determine the amount
L
i
F  2 kx 1 

x L 

of work done by this force
in moving the particle from
x = A to x = 0.
2
2
Review problem. A particle of mass
0.500 kg is shot from P as shown in
Figure P7.6. The particle has an initial
velocity with a horizontal component of
30.0 m/s. The particle rises to a
maximum height of 20.0 m above P.
Determine (a) the vertical component of

v i, (b) the work done by the gravitational
force on the particle during its motion
from P to B, and (c) the horizontal and
the vertical components of the velocity
vector when the particle reaches B.