Question

9- a rock moving 600 km/min, traveling in a south- to- north direction passed near earth in 2013. which statement describes the meteor’s motion? (1 minute= 60 seconds)
a. its velocity was 10 km/s northward
b. its acceleration was 600 km/s²
c. its speed was 600 km/s northward
d. its acceleration was 10 km/s²
i chose ____ because __________

Explanation:

Step1: Convert speed units

The rock's speed is \( 600 \, \text{km/min} \). To convert to \( \text{km/s} \), use the conversion factor \( 1 \, \text{min} = 60 \, \text{s} \). So, \( 600 \, \text{km/min} = \frac{600 \, \text{km}}{60 \, \text{s}} = 10 \, \text{km/s} \).

Step2: Analyze velocity, speed, and acceleration

• Velocity is speed with direction. The rock moves south - to - north, so velocity is \( 10 \, \text{km/s} \) northward.
• Speed is a scalar (no direction), so option C is wrong (speed can't have direction).
• Acceleration is a change in velocity. There's no info about velocity change, so options B and D (about acceleration) are wrong.

Answer:

A. Its velocity was 10 km/s northward
I chose A because we convert the speed \( 600 \, \text{km/min} \) to \( 10 \, \text{km/s} \) (using \( 1 \, \text{min} = 60 \, \text{s} \)), velocity includes direction (northward here), speed (option C) can't have direction, and no info about acceleration (so B, D wrong).