Question

remember that the change in a quantity is always the final amount minus the initial amount. the impulse - momentum theorem also tells us that the direction of the impulse is the same as the direction of the change in momentum.

critical thinking questions, part 1
the picture below shows a collision about to happen between two railroad cars. car #1 has a mass of 2000 kg and is traveling to the right at 4 m/s, while the car #2 has a mass of 1000 kg and is traveling to the left at 2 m/s. assume friction is negligible.

1. what is the initial magnitude and direction of the momentum of car #1?

Explanation:

Step1: Recall momentum formula

The formula for momentum is $p = mv$, where $p$ is momentum, $m$ is mass and $v$ is velocity.

Step2: Identify values for car #1

For car #1, $m = 2000$ kg and $v=4$ m/s (positive since it's moving to the right).

Step3: Calculate momentum

$p_1=mv = 2000\times4=8000$ kg·m/s. The direction is to the right.

Answer:

The magnitude of the initial momentum of car #1 is 8000 kg·m/s and the direction is to the right.