Unlock document.
This document is partially blurred.
Unlock all pages and 1 million more documents.
Get Access
PROBLEM 12.24
An airplane has a mass of 25 Mg and its engines develop a total thrust of 40 kN during take-off. If the drag
D exerted on the plane has a magnitude 2
2.25 ,
D
v where v is expressed in meters per second and D in
newtons, and if the plane becomes airborne at a speed of 240 km/h, determine the length of runway required
for the plane to take off.
PROBLEM 12.25
A 4-kg projectile is fired vertically with an initial velocity of 90 m/s, reaches a maximum height and falls to
the ground. The aerodynamic drag
D
has a magnitude D = 0.0024
2
v
where D and v are expressed in newtons
and m/s, respectively. Knowing that the direction of the drag is always opposite to the direction of the
velocity, determine (a) the maximum height of the trajectory, (b) the speed of the projectile when it reaches
the ground.
Copyright © McGraw-Hill Education. Permission required for reproduction or display.
PROBLEM 12.25 (Continued)
PROBLEM 12.26
A constant force P is applied to a piston and rod of total mass m to
make them move in a cylinder filled with oil. As the piston moves, the
oil is forced through orifices in the piston and exerts on the piston a
force of magnitude kv in a direction opposite to the motion of the
piston. Knowing that the piston starts from rest at 0t and
0,x
show that the equation relating x, v, and t, where x is the distance
traveled by the piston and v is the speed of the piston, is linear in each
of these variables.
PROBLEM 12.27
A spring AB of constant k is attached to a support at A and to a
collar of mass m. The unstretched length of the spring is .
Knowing that the collar is released from rest at
0
x
x
and
neglecting friction between the collar and the horizontal rod,
determine the magnitude of the velocity of the collar as it passes
through Point C.
PROBLEM 12.28
Block A has a mass of 10 kg, and blocks B and C have masses of 5 kg each.
Knowing that the blocks are initially at rest and that B moves through 3 m in 2 s,
determine (a) the magnitude of the force
P
, (b) the tension in the cord AD. Neglect
the masses of the pulleys and axle friction.
PROBLEM 12.28 (Continued)
PROBLEM 12.29
A 40-lb sliding panel is supported by rollers at B and C. A 25-lb counterweight A is attached to a cable as
shown and, in cases a and c, is initially in contact with a vertical edge of the panel. Neglecting friction,
determine in each case shown the acceleration of the panel and the tension in the cord immediately after the
system is released from rest.
PROBLEM 12.29 (Continued)
PROBLEM 12.30
An athlete pulls handle A to the left with a constant
force of P = 100 N. Knowing that after the handle
A has been pulled 30 cm its velocity is 3 m/s,
determine the mass of the weight stack B.
