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A printable worksheet for the lesson The energy of impacts and airbursts (A-level). It prints on A4 without the website around it. The answers are on a separate sheet for the teacher.

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A-level · Ages 16 to 18 (Years 12 and 13)Howardites worksheet

The energy of impacts and airbursts

Name:Class:Date:

Key words

Airburst
An airburst is when an incoming space rock explodes in the atmosphere instead of hitting the ground in one piece.
Density
Density is how much mass is packed into a given volume, and most meteorites are denser than typical Earth rocks.
Meteor
A meteor is the streak of light you see when a meteoroid burns up in Earth's air.
Central peak
A mountain or cluster of hills in the middle of a complex crater, made of rock pushed up from deep below.
Peak ring
A circle of mountains inside a large impact crater, found instead of a single central peak.

Choose the right answer

Circle the letter of the right answer.

  1. Why does crater diameter grow much more slowly than impact energy?
    • ACrater diameter depends only on the impactor's density
    • BMost of the energy is always lost as light
    • CLarger impactors are always slower
    • DGravity and target strength limit how much rock can be excavated
  2. A stony asteroid 20 m across enters the atmosphere at 19 km s⁻¹. What is the most likely outcome?
    • AIt bounces off the atmosphere back into space
    • BIt fragments and explodes in the atmosphere
    • CIt slows gently and lands without damage
    • DIt reaches the ground intact and makes a large crater
  3. What is the energy of the Chelyabinsk airburst, about 0.5 Mt, in joules?
    • AAbout 2.1 × 10¹⁵ J
    • BAbout 4.2 × 10¹⁵ J
    • CAbout 8.4 × 10¹⁵ J
    • DAbout 1.2 × 10⁻¹⁶ J
  4. At the same size and speed, how much more kinetic energy does an iron impactor (7,800 kg m⁻³) carry than a stony one (3,000 kg m⁻³)?
    • AAbout 2.6 times
    • BThe same, because energy depends only on speed
    • CAbout 1.6 times
    • DAbout 6.8 times
  5. What happens to impact craters larger than a few kilometres across on Earth?
    • AThey always form a ring of mountains outside the rim
    • BThey fill with melt and leave no rim
    • CThey collapse under gravity into complex craters
    • DThey stay as simple bowls but grow deeper

True or false?

Is the answer given right? Tick True or False.

  1. Which list puts these in order of energy, lowest first?

    Answer given: 1 kt blast, Chelyabinsk, 50 m stony body at 17 km s⁻¹, Tunguska TrueFalse

  2. In the activity, why are the outcomes for a 50 m stony body and a 50 m iron body so different?

    Answer given: Iron is denser and much stronger, so it can reach the ground TrueFalse

Write your answer

Answer in a word or a short sentence.

  1. Why is the mass of a spherical impactor of diameter d written as m = ρ × (π/6)d³?
  2. An impactor's speed doubles while its size and density stay the same. By what factor does its kinetic energy change?
  3. A 1.0 × 10⁶ kg body strikes at 2.0 × 10⁴ m s⁻¹. What is its energy in kilotonnes of TNT? (1 kt = 4.184 × 10¹² J)

Task

Use the impact calculator on this site to find the energy of a 50 m stony body (density 3,000 kg m⁻³) at 17 km s⁻¹, then check it by hand. Repeat for an iron body (7,800 kg m⁻³). Explain why the outcomes predicted by the calculator differ so much for the two compositions.

Howardites · free to copy for use in your classroom · answers are on the separate teacher's answer sheet