Neil Armstrong, the first man to walk on the moon, described seeing the Earth as follows: All of a sudden, you could see the whole sphere - Leaving Cert Physics - Question 6 - 2019

A vector quantity has both magnitude and direction, while a scalar quantity only has magnitude. For example:

• Vector quantity: Velocity (e.g., 60 km/h north)
• Scalar quantity: Speed (e.g., 60 km/h)

This distinction is crucial in physics, especially in understanding motion and forces.

An astronaut has a constant speed if they are moving in a circular path at a regular rate. However, velocity is a vector, which means it takes into account both speed and direction. As the astronaut moves in orbit, their direction constantly changes, which results in a changing velocity, even though their speed remains constant.

Weight can be calculated using the formula:

$W = m \cdot g$

where:

• $m = 90$ kg (mass)
• $g = 9.8$ m/s² (acceleration due to gravity)

Substituting the values:

$W = 90 \cdot 9.8 = 882 \text{ N}$

Therefore, Armstrong's weight on Earth is $882$ N.

Mass does not change with location; therefore, Armstrong's mass on the moon remains the same:

$90\, \text{kg}$.

Weight is dependent on gravitational force, which varies depending on celestial bodies. The moon's gravitational force is approximately 1/6th that of Earth's. Thus, Armstrong's weight on the moon can be calculated as:

$W_{moon} = 0.17 \times W_{Earth} = 0.17 \times 882 \approx 150 \text{ N}$

This lower weight reflects the moon's weaker gravitational pull.

Pressure is defined as the force exerted per unit area. The formula for pressure is:

$P = \frac{F}{A}$

where:

• $P$ is pressure,
• $F$ is force, and
• $A$ is area.

Using the formula for pressure:

$P = \frac{F}{A}$

Assuming Armstrong's weight on the moon is approximately $150$ N (as calculated in part vi) and the area of his shoe is $0.03$ m², substituting the values gives:

$P = \frac{150}{0.03} = 5000 \text{ Pa}$

Hence, the pressure Armstrong exerted on the moon's surface is $5000$ Pa.