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. A great, gigantic, blue ball, covered with a white lace of clouds. It was spectacular. Armstrong’s love of flying started at a young age. After joining the navy he became a fighter pilot. (i) A jet starts from rest and accelerates along a runway to a top speed of 28 m s−1 in 7 seconds. What is the acceleration of the jet? (9) (ii) Acceleration is a vector quantity, while time is a scalar quantity. Distinguish between a vector quantity and a scalar quantity. (6) (iii) The moon is constantly in motion, orbiting the Earth. Explain why an astronaut standing on the moon has a constant speed but a changing velocity. (6) Armstrong applied to become an astronaut and in 1962 he joined NASA. (iv) Armstrong had a mass of 90 kg. Calculate his weight on Earth. Include units in your answer. (9) (v) What was Armstrong's mass on the moon? (6) (vi) Armstrong's weight on the moon was only 17% of his weight on Earth. Explain why. (20) On July 21st 1969, Armstrong became the first man to walk on the moon. An estimated 530 million people watched him. The footprints he made during that walk are still on the moon to this day. The area of Armstrong's shoe when he took that famous step was 0.03 m². He exerted pressure through his foot onto the surface of the moon. (vii) Define pressure. (3) (viii) Calculate the pressure Armstrong exerted on the surface of the moon. (acceleration due to gravity, g = 9.8 m s²)

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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

Question 6

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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. A great, gigantic, blue b... show full transcript

Worked Solution & Example Answer: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

Step 1

i) A jet starts from rest and accelerates along a runway to a top speed of 28 m s−1 in 7 seconds. What is the acceleration of the jet?

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Answer

To calculate acceleration, we use the formula:

$a = \frac{v - u}{t}$

where:

$v = 28$ m/s (final velocity)
$u = 0$ m/s (initial velocity, starting from rest)
$t = 7$ s (time)

Substituting the values:

$a = \frac{28 - 0}{7} = \frac{28}{7} = 4\, \text{m/s}^2$

Thus, the acceleration of the jet is $4\, \text{m/s}^2$ .

Step 2

ii) Acceleration is a vector quantity, while time is a scalar quantity. Distinguish between a vector quantity and a scalar quantity.

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Answer

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.

Step 3

iii) The moon is constantly in motion, orbiting the Earth. Explain why an astronaut standing on the moon has a constant speed but a changing velocity.

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Answer

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.

Step 4

iv) Armstrong had a mass of 90 kg. Calculate his weight on Earth. Include units in your answer.

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Answer

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.

Step 5

v) What was Armstrong's mass on the moon?

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Answer

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

$90\, \text{kg}$ .

Step 6

vi) Armstrong's weight on the moon was only 17% of his weight on Earth. Explain why.

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Answer

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.

Step 7

vii) Define pressure.

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Answer

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.

Step 8

viii) Calculate the pressure Armstrong exerted on the surface of the moon.

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Answer

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.

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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

Worked Solution & Example Answer: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

i) A jet starts from rest and accelerates along a runway to a top speed of 28 m s−1 in 7 seconds. What is the acceleration of the jet?

ii) Acceleration is a vector quantity, while time is a scalar quantity. Distinguish between a vector quantity and a scalar quantity.

iii) The moon is constantly in motion, orbiting the Earth. Explain why an astronaut standing on the moon has a constant speed but a changing velocity.

iv) Armstrong had a mass of 90 kg. Calculate his weight on Earth. Include units in your answer.

v) What was Armstrong's mass on the moon?

vi) Armstrong's weight on the moon was only 17% of his weight on Earth. Explain why.

vii) Define pressure.

viii) Calculate the pressure Armstrong exerted on the surface of the moon.

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