Page 365 - Dynamics of Mechanical Systems

0593_C10_fm Page 346 Monday, May 6, 2002 2:57 PM

346 Dynamics of Mechanical Systems

H

7 ft
C
F
FIGURE P10.2.5
A force F pushing a cart up a hill. 27 ft

P10.2.6: A force pushes a block B along a smooth horizontal slot from a position O to a
position Q as in Figure P10.2.6. The movement of B is resisted by a linear spring with a
natural (unstretched) length of 6 in. and modulus 12 lb/in. Determine the work done by F.

k = 12 lb/in.
6 in.

F B B
FIGURE P10.2.6 O Q
A block sliding in a slot. 8 in.

P10.2.7: Repeat Problem P10.2.6 if the natural length of the spring is 4 in.
P10.2.8: A motorist, in making a turn with a 15-in.-diameter steering wheel, exerts a force
of 8 lb with each hand tangent to the wheel as in Figure P10.2.8. If the wheel is turned
through an angle of 150°, determine the work done by the motorist.

8 lb
15 in. diameter

FIGURE P10.2.8
8 lb
Forces on a steering wheel.

Section 10.4 Power
P10.4.1: An automobile with a 110-hp engine is traveling at 35 mph. If there are no frictional
losses in the transmission or drive train, what is the tractive force exerted by the drive
wheels?
P10.4.2: See Problem P10.4.1. Suppose the automobile of Problem P10.4.1 has 26-in.-
diameter drive wheels, a transmission gear ratio of 8 to 1, and a drive axle gear ratio of
4.5 to 1. What is the engine speed (in rpm)? What is the torque (in ft⋅lb) of the engine
crank shaft?