Fizik
Collisions
Inelastic Collisions Elastic Collisions Stationary Target Moving Target Collisions in 2-Dimensions (Glancing Collisions)
Inelastic Collisions
Collisions in which kinetic energy is not conserved. Initial kinetic energy is transformed into other types of energy (thermal, potential etc.) Total final kinetic energy is less than the total initial kinetic energy. If two objects stick together as a result of the collision, the collisions is inelastic. Even though the kinetic energy is not conserved, the total energy is conserved.
1-Dimensional Inelastic Collisions
When one body is initially stationary, the law of conservation states that
������������ ������������ + ������������ ������������ =
������������ + ������������ ������
Taken m2 is at rest, and V is the final velocity of the stuck together bodies then
������ =
������������ ������������ + ������������
������������
Before Collision
m1
v
m2 at rest +x
m1 + m 2 V After Collision
1-Dimensional Inelastic Collisions
When both of the bodies are moving, the law of conservation states that
������������ ������������ + ������������ ������������ =
������������ + ������������ ������
The final velocity of the stuck together bodies is given as
������ =
������������ ������������ + ������������ ������������ ������������ + ������������
EXAMPLE
A ballistic pendulum is a device that was used to measure the speeds of bullets before electronic timing devices were developed. The device consists of a large block of wood of mass M = 5.4 kg, hanging from two long cords. A bullet of mass m = 9.5 g is fired into the block, coming quickly to rest. The block + bullet swing upward, their center of mass rising a vertical distance h = 6.3 cm before the pendulum comes momentarily to rest. (a) What was the speed v of the bullet just prior to the collisions. (b) What is the initial kinetic energy? How much energy remains as mechanical energy?
Inelastic Collisions Elastic Collisions Stationary Target Moving Target Collisions in 2-Dimensions (Glancing Collisions)
Inelastic Collisions
Collisions in which kinetic energy is not conserved. Initial kinetic energy is transformed into other types of energy (thermal, potential etc.) Total final kinetic energy is less than the total initial kinetic energy. If two objects stick together as a result of the collision, the collisions is inelastic. Even though the kinetic energy is not conserved, the total energy is conserved.
1-Dimensional Inelastic Collisions
When one body is initially stationary, the law of conservation states that
������������ ������������ + ������������ ������������ =
������������ + ������������ ������
Taken m2 is at rest, and V is the final velocity of the stuck together bodies then
������ =
������������ ������������ + ������������
������������
Before Collision
m1
v
m2 at rest +x
m1 + m 2 V After Collision
1-Dimensional Inelastic Collisions
When both of the bodies are moving, the law of conservation states that
������������ ������������ + ������������ ������������ =
������������ + ������������ ������
The final velocity of the stuck together bodies is given as
������ =
������������ ������������ + ������������ ������������ ������������ + ������������
EXAMPLE
A ballistic pendulum is a device that was used to measure the speeds of bullets before electronic timing devices were developed. The device consists of a large block of wood of mass M = 5.4 kg, hanging from two long cords. A bullet of mass m = 9.5 g is fired into the block, coming quickly to rest. The block + bullet swing upward, their center of mass rising a vertical distance h = 6.3 cm before the pendulum comes momentarily to rest. (a) What was the speed v of the bullet just prior to the collisions. (b) What is the initial kinetic energy? How much energy remains as mechanical energy?