1. Which of the following is not a correct statement.
   1. If colliding objects are treated as a single system, then the net force acting on the system is zero.
   2. The impulse acting on an object is equal to the change of momentum of the object.
   3. Momentum of colliding objects is always conserved.
   4. If the net force acting on an object is zero, then its momentum is conserved.
   5. During a completely elastic collision, some of the kinetic energy of the colliding objects is converted to heat energy.
2. Calculate the momentum of an object of mass 18 kg if its kinetic energy is 60 J.
3. After a bullet of mass 0.035 kg is fired into a ballistic pendulum of mass 1.5 kg, the bullet is embedded in the pendulum and the pendulum rose to a height of 0.1 m. Calulate the speed with which the bullet was fired into the ballistic pendulum.
4. An object of mass 9 kg going to the right with a speed of 12 m s collides with a(n) 16 kg object at rest. If the collision is completely elastic, calculate the speed of the 16 kg object after collision.
5. An object of mass 3 kg going to the right with a speed of 24 m s collides with a(n) 8 kg object going in the same direction with a speed of 29 m s. If the collision is completely elastic, calculate the speed of the 8 kg object after collision.
6. An object of mass 19 kg going to the right with a speed of 29 m s collides with a(n) 12 kg object at rest. After collision the 19 kg object moves with a speed of 19 m s making an angle of 60 degree with the horizontal-right. Calculate the x-component of the velocity of the 12 kg object after collision.
7. An object of mass 7 kg going to towards north with a speed of 28 m s collides with a(n) 28 kg object going east with a speed of 33 m s. After collision the 7 kg object moves with a speed of 11 m s making an angle of 50 degree with the horizontal-right. Calculate the magnitude and direction of the velocity of the 28 kg object after collision.
   1. 39.027 m s, 7.431 deg
   2. 29.906 m s, 8.905 deg
   3. 31.613 m s, 8.905 deg
   4. 28.452 m s, 10.102 deg
   5. 31.613 m s, 10.102 deg