Momentum-Impulse Theorem

Collision:

If no external force, momentum always conserved.

fi pp

ifif vmvmppptFI

Is the kinetic energy conserved?

Inelastic collision fi pp

fi KK

Completely inelastic collision: stick together

fii vmmvmvm

)( 212211

Elastic collision fi pp

fi KK

222

211

222

211

22112211

2

1

2

1

2

1

2

1ffii

ffii

vmvmvmvm

vmvmvmvm

21

212112

21

121221

2211

)(2

)(2

mm

vmmvmv

mm

vmmvmv

vvvv

iif

iif

fifi

If v1i ,v2i is same direction

Object sticks to together:

1200-kg car moving at 2.5 m/s is struck in the rear by a 2600-kg truck moving at 6.2 m/s. If the vehicles stick together the collision, what is their speed immediately after colliding? (assume that external forces may be ignored).

2600 kg

1200 kg

6.2 m/s 2.5 m/svf

Ballistic Pendulum

In a ballistic pendulum, an object of mass m is fired with an initial speed v0 at the bob of a pendulum. The bob has a mass M, and is suspended by a rod of negligible mass. After the collision, the object and the bob stick together and swing to through an arc, eventually gaining a height h. Find h in terms of m, M, v0, and g

collision in 2D

m1=950 kgm2=1300kg

Completely Inelastic collision

Elastic collision:

fi

fi

KK

pp

96 kg

135 kg

1.24 m/s 0 m/s

96 kg

135 kg

Find the final velocity of the car?