978-0077687342 Chapter 13 Part 17

PROBLEM 13.CQ5

The expected damages associated with two types of perfectly plastic collisions are to be

compared. In the first case, two identical cars traveling at the same speed impact each

other head on. In the second case, the car impacts a massive concrete wall. In which case

would you expect the car to be more damaged?

(a) Case 1

(b) Case 2

(c) The same damage in each case

SOLUTION

PROBLEM 13.CQ6

A 5 kg ball A strikes a 1 kg ball B that is initially at rest. Is it

possible that after the impact A is not moving and B has a speed

of 5v?

(a) Yes

(b) No

Explain your answer.

SOLUTION

PROBLEM 13.F1

The initial velocity of the block in position A is 30 ft/s. The coefficient

of kinetic friction between the block and the plane is

m

k = 0.30. Draw

impulse–momentum diagrams that could be used to determine the time

it takes for the block to reach B with zero velocity, if

θ

= 20°.

SOLUTION

PROBLEM 13.F2

A 4–lb collar which can slide on a frictionless vertical rod is

acted upon by a force P which varies in magnitude as shown.

Knowing that the collar is initially at rest, draw impulse–

momentum diagrams that could be used to determine its

velocity at t = 3 s.

SOLUTION

1

0

t

=



PROBLEM 13.F3

The 15–kg suitcase A has been

propped up against one end of a

40-kg luggage carrier B and is

prevented from sliding down by

other luggage. When the luggage

is unloaded and the last heavy

trunk is removed from the carrier,

the suitcase is free to slide down,

causing the 40-kg carrier to move

to the left with a velocity vB of

magnitude 0.8 m/s. Neglecting

friction, draw impulse-momentum

diagrams that could be used to

determine (a) the velocity of A as

it rolls on the carrier and (b) the

velocity of the carrier after the

suitcase hits the right side of the

carrier without bouncing back.

SOLUTION

Answer:

PROBLEM 13.F4

Car A was traveling west at a speed of 15 m/s and car B was traveling north at an

unknown speed when they slammed into each other at an intersection. Upon

investigation it was found that after the crash the two cars got stuck and skidded

off at an angle of 50° north of east. Knowing the masses of A and B are mA and mB

respectively, draw impulse–momentum diagrams that could be used to determine

the velocity of B before impact.

SOLUTION

Answer:

PROBLEM 13.F5

Two identical spheres A and B, each of mass m, are attached to an inextensible

inelastic cord of length L and are resting at a distance a from each other on a

frictionless horizontal surface. Sphere B is given a velocity v0 in a direction

perpendicular to line AB and moves it without friction until it reaches B’ where the

cord becomes taut. Draw impulse–momentum diagrams that could be used to

determine the magnitude of the velocity of each sphere immediately after the cord

has become taut.

yy

AB

PROBLEM 13.F6

A sphere with a speed v0 rebounds after striking a frictionless inclined plane as

shown. Draw impulse-momentum diagrams that could be used to find the velocity

of the sphere after the impact.

SOLUTION

Answer:

PROBLEM 13.F7

An 80-Mg railroad engine A

coasting at 6.5 km/h strikes a 20-

Mg flatcar C carrying a 30–Mg

load B which can slide along the

floor of the car (mk = 0.25). The

flatcar was at rest with its brakes

released. Instead of A and C

coupling as expected, it is observed

that A rebounds with a speed of 2

km/h after the impact. Draw

impulse–momentum diagrams that

could be used to determine (a) the

coefficient of restitution and the

speed of the flatcar immediately

after impact, and (b) the time it

takes the load to slide to a stop

relative to the car.

SOLUTION

Answer:

(a) Look at A and C (the friction force between B and C is not impulsive) to find the velocity after impact.

PROBLEM 13.F8

Two frictionless balls strike each other as shown. The coefficient of restitution

between the balls is e. Draw the impulse–momentum diagrams that could be used

to find the velocities of A and B after the impact.

SOLUTION

Answer:

PROBLEM 13.F9

A 10-kg ball A moving horizontally at 12 m/s strikes a 10-kg block B. The

coefficient of restitution of the impact is 0.4 and the coefficient of kinetic

friction between the block and the inclined surface is 0.5. Draw impulse-

momentum diagrams that could be used to determine the speeds of A and B

after the impact.

SOLUTION

Answer:

PROBLEM 13.F10

Block A of mass mA strikes ball B of mass mB with a speed of vA as shown.

Draw impulse–momentum diagrams that could be used to determine the speeds

of A and B after the impact and the impulse during the impact.

SOLUTION

Answer: