3. Curious George observed an interesting event in an international toy exhibition . Two toy cars were moving forward in a monorail. Toy car #1, weighing 10 kg. was ahead of toy car #2, weighing 20 kg. in the beginning . but they collided and joined together . The initial velocity of toy car #1 is 10 m/s and that of toy car #2 is 20 m/s. What is the final velocity of both of these cars after they are connected ? Assume that there is no friction in this system . Hint : See Sample Question 3 in the Unit IV Lesson and Example 5 on page 181 to 182 in the textbook 4. In an isolated system . a 2kg ball with an initial velocity of 3 m/s hits a 5 kg ball that is initially at rest . What is the total kinetic energy before the collision ? If the total kinetic energy after the collision is the