1.A moving ball(1) collides elastically with an identical stationary ball (2). B

Question

1.A moving ball(1) collides elastically with an identical stationary ball (2). Ball(2) shoots off to the right along the x axis. What is the final velocity of ball(1) and the final speed of ball (2)?

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2.a massless rigid rod with x1=0, m1=6kg, x2=1, m2=2kg

a.what is xc the centre of mass?

b.A force 8*10^10Ng^ (upward) hits m2 for deltaT=10^-10s.

the instant after, what is the final velocity of m2?

c.what is the final velocity of the center of mass and the final angular velocity about the centre of mass?

Explanation / Answer

Here an object starts with 20 units (kg•m/s) of momentum. It then encounters an impulse of 60 units (N•s) in the direction of motion. A 60-unit impulse will change the momentum by 60 units, either increasing or decreasing it. If the impulse is in the direction of an object's motion, then it will increase the momentum. So now the object has 80 units (kg•m/s) of momentum. The object then encounters a resistive force of 6.0 N for 8.0 s. This is equivalent to an impulse of 48 units (N•s). Since this impulse is "resistive" in nature, it will decrease the object's momentum by 48 units. The object now has 32 units of momentum. The question asks for the object's velocity after encountering these two impulses. Since momentum is the product of mass and velocity, the velocity can be easily determined.

Here the object begins with a momentum of 18 units (kg•m/s). The object encounters a force of 2.5 N for 8.0 seconds. This is equivalent to an impulse of 20 units (N•s). Since this impulse acts in the direction of motion, it changes the object's momentum from 18 units to 38 units. A final impulse is encountered when colliding with a wall. Upon rebounding, the object has a momentum of -15 units (kg•m/s). The -15 is the product of mass (3 kg) and velocity (-5 m/s). The "-" sign is used since the object is now moving in the opposite direction as the original motion. The collision with the wall changed the object's momentum from +38 units to -15 units. Thus, the collision must have resulted in a 53-unit impulse since it altered the object's momentum by 53 units.

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