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

Acceleration is a vector quantity because it has both magnitude and direction, while time is a scalar quantity as it only has magnitude without any direction.

Vector quantities have both magnitude and direction, for example, velocity and force. Scalar quantities only have magnitude, like temperature and mass.

An astronaut has constant speed because the magnitude of their velocity remains the same; however, the direction changes as they move in a circular path around the Earth, resulting in a changing velocity.

The weight of an object can be calculated using the formula:

$W = m \cdot g$

where:

• $m = 90 \, \text{kg}$ , (mass)
• $g = 9.8 \, \text{m s}^{-2}$ , (acceleration due to gravity)

Therefore,

$W = 90 \, \text{kg} \cdot 9.8 \, \text{m s}^{-2} = 882 \, \text{N}$

Thus, Armstrong's weight on Earth is $882 \, \text{N}$.

Armstrong's mass remains the same regardless of location, so his mass on the moon is still $90 \, \text{kg}$.

Armstrong's weight on the moon is lower due to the moon's weaker gravitational pull compared to Earth. The acceleration due to gravity on the moon is approximately $1.625 \, \text{m s}^{-2}$, which is about $1/6$ of Earth's gravity.

Pressure can be calculated using the formula:

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

where:

• $F$ is the force, which is equal to Armstrong's weight on the moon. With his weight being $150.6 \, \text{N}$ (17% of $882 \, \text{N}$) and $A = 0.03 \, \text{m}^2$:

$P = \frac{150.6 \, \text{N}}{0.03 \, \text{m}^2} = 5020 \, \text{Pa}$

Thus, the pressure exerted by Armstrong on the surface of the moon is approximately $5020 \, \text{Pa}$.