What is the momentum of a bullet of mass 8.0 g fired from a rifle at 689 km/h? Give your answer to one decimal place.

Question

BlackTom AI · Accepted Answer

Momentum p = m v, so use mass in kilograms and speed in metres per second to compute p in kg·m/s (same as N·s).

1) Relevant knowledge points and concepts
- Linear momentum p is defined as p = m v.
- SI units: mass in kilograms (kg) and velocity in metres per second (m/s).
- Convert grams to kilograms (1 g = 0.001 kg) and kilometres per hour to metres per second (1 km/h = 1/3.6 m/s).
- Final answer rounded to one decimal place.

2) Step-by-step reasoning
- Convert the mass: 8.0 g → 8.0 × 0.001 = 0.008 kg.
- Convert the speed: 689 km/h → 689 ÷ 3.6 m/s.

3) Calculations (all intermediate steps)
- Velocity: 689 ÷ 3.6 = 191.3888889 m/s (repeating).
- Momentum: p = m v = 0.008 kg × 191.3888889 m/s
- Multiply: 0.008 × 191.3888889 = 1.531111111 kg·m/s.

4) Why the correct answer is correct
- Using proper unit conversions and the standard momentum formula yields p ≈ 1.5311 kg·m/s. Rounding this to one decimal place (look at the second decimal digit: 3) gives 1.5 kg·m/s. This is the correct value with correct units and rounding.

5) Why other answers would be incorrect
- Common mistakes: failing to convert grams to kilograms (would give 1000× larger numeric value, e.g., 1531.1 but with incorrect units), or failing to convert km/h to m/s (using 689 as if m/s gives 0.008×689 = 5.512, which uses inconsistent units). Any answer not equal to 1.5 kg·m/s indicates a unit-conversion or arithmetic error.

6) Conclusion
- Confirmed final answer (to one decimal place): 1.5 (kg·m/s).

What is the momentum of a bullet of mass 8.0 g fired from a rifle at 689 km/h? Give your answer to one decimal place.数值题

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