Calculus-Based Physics by Jeffrey W. Schnick - HTML preview

Chapter 4 Conservation of Momentum

Example 4-1

Two objects move on a horizontal frictionless surface along the same line in the same

direction which we shall refer to as the forward direction. The trailing object of mass

2.0 kg has a velocity of 15 m/s forward. The leading object of mass 3.2 kg has a

velocity of 11 m/s forward. The trailing object catches up with the leading object and the

two objects experience a completely inelastic collision. What is the final velocity of each

of the two objects?

BEFORE

AFTER

m

v

m

= 15

v = 11

v ′

1

2

s

1

s

2

1

2

m = 2.0 kg

m = 3.2 kg

1

2

Σp = Σ ′

→

→

p

p + p = ′

p

1

2

12

mv + m v = (m + m )v ′

1 1

2 2

1

2

mv + m v

1 1

2

2

v ′ = m +m

1

2

2.0 kg 15

(

m / s) + 3 2

. kg 11

(

m / s)

v ′ =

2.0 kg + 3 2

. kg

m

v ′ =12 54

.

s

m

v ′ =13 s

m

The final velocity of each of the objects is 13

forward.

s

23