Momentum Basics Quiz

Momentum Basics

• Momentum (p) is defined as the product of an object's mass (m) and its velocity (v): p = m × v.
• Example: A dinosaur with a mass of 4,500 kg traveling at 12 m/s has a momentum of 54,000 kg·m/s.
• Example: A car with a mass of 1,200 kg traveling at 25 m/s has a momentum of 30,000 kg·m/s.
• Momentum is a vector quantity, meaning it has both magnitude and direction.

Positive and Negative Momentum

• If a direction is defined as positive (e.g., right), the dinosaur carries positive momentum and the car negative momentum when heading towards each other.

Conservation of Momentum

• In a closed system, total momentum before an event (like a collision) equals total momentum after the event.
• For the dinosaur and car example, pre-collision momentum is calculated: 54,000 kg·m/s (dinosaur) + (-30,000 kg·m/s) (car) = 24,000 kg·m/s total momentum (to the right).

Post-Collision Velocity

• After their collision, the combined object maintains the total momentum of 24,000 kg·m/s.
• Combined mass of dinosaur and car: 4,500 kg + 1,200 kg = 5,700 kg.
• Using momentum equation: velocity (v) = momentum (p) / mass (m) results in v = 24,000 kg·m/s / 5,700 kg = 4.4 m/s to the right.

Zero Momentum Scenario

• Objects at rest have zero momentum. For example, a stationary gun has zero initial momentum.
• When the gun fires, the bullet gains forward momentum while the gun recoils backward with equal momentum to maintain a total momentum of zero.

Gun and Bullet Example

• A 5-gram bullet (0.005 kg) fired at a velocity of 120 m/s has a momentum of 0.6 kg·m/s.
• For the gun (2 kg), let its recoil velocity be v; its momentum is 2v.
• The equation for the total momentum: 2v + 0.6 = 0 leads to determining the recoil velocity of the gun.
• Rearranging gives: 2v = -0.6, resulting in v = -0.3 m/s (direction opposite to the bullet's momentum).

Momentum Notation

• The symbol for momentum is p, leading to the equation: p = mv.

Momentum Basics

• Momentum (p) is the product of mass (m) and velocity (v): p = m × v.
• A dinosaur with a mass of 4,500 kg traveling at 12 m/s has momentum: 54,000 kg·m/s.
• A car with a mass of 1,200 kg traveling at 25 m/s has momentum: 30,000 kg·m/s.
• Momentum is a vector quantity, meaning it has direction as well as magnitude.

Positive and Negative Momentum

• If a rightward direction is defined as positive, a dinosaur moving right has positive momentum, while a car moving left has negative momentum when approaching each other.

Conservation of Momentum

• In a closed system, total momentum before an event equals total momentum after the event.
• For the dinosaur and car collision, pre-collision momentum is: 54,000 kg·m/s (dinosaur) + (-30,000 kg·m/s) (car) = 24,000 kg·m/s (to the right).

Post-Collision Velocity

• After the collision, the combined object retains momentum of 24,000 kg·m/s.
• The combined mass of the dinosaur and car is: 4,500 kg + 1,200 kg = 5,700 kg.
• Use momentum equation to find velocity: v = 24,000 kg·m/s / 5,700 kg = 4.4 m/s to the right.

Zero Momentum Scenario

• Objects at rest possess zero momentum.
• A stationary gun has zero initial momentum.
• Upon firing, the bullet gains forward momentum while the gun recoils backward with equal momentum, preserving a total momentum of zero.

Gun and Bullet Example

• A bullet weighing 5 grams (0.005 kg) fired at 120 m/s has momentum: 0.6 kg·m/s.
• For the 2 kg gun, if the recoil velocity is v, its momentum is expressed as 2v.
• Setting up the total momentum equation: 2v + 0.6 = 0 allows determination of the gun's recoil velocity.
• Solving gives 2v = -0.6, resulting in v = -0.3 m/s (in the opposite direction of the bullet's momentum).

Momentum Notation

• The symbol for momentum is p.
• The fundamental momentum equation is expressed as: p = mv.