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Grade 8: Science subject test

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1. Supplied case 6: total distance (m)=72; elapsed time (s)=8, using the explicitly named quantities. Average speed equals distance in meters divided by time in seconds. What result follows?576 m/s10 m/s8 m/s9 m/s

2. Supplied case 6: mass (kg)=2.5; signed velocity (m/s)=-4, using the explicitly named quantities. Momentum equals mass in kilograms multiplied by signed velocity in meters per second. What result follows?-9 kg·m/s-11 kg·m/s-10 kg·m/s-1.5 kg·m/s

3. Supplied case 6: first signed momentum (kg·m/s)=-12; second signed momentum (kg·m/s)=-4, using the explicitly named quantities. Total momentum equals the two signed supplied momenta added. What result follows?-17 kg·m/s-16 kg·m/s-8 kg·m/s-15 kg·m/s

4. Position remains 7 m from time 3 s to 8 s. What is supported? Which inference or prediction is best supported?The segment has zero velocity despite five seconds elapsing.The object moves 7 m each second.Five seconds proves five meters traveled.A horizontal segment means infinite speed.

5. A full phase and a quarter phase occur with sunlight reaching half the Moon in both models. What changed? Which inference or prediction is best supported?The Moon’s total sunlight must switch from full to half.The Moon must produce its own varying light.The Earth-viewing angle on the illuminated half changed.Earth necessarily blocked more sunlight at quarter.

6. A supplied Sun-Moon-Earth alignment sends the Moon’s shadow onto Earth. What event can occur there? Which inference or prediction is best supported?An eclipse everywhere on Earth regardless of shadow location.A solar eclipse where the shadow geometry permits it.A lunar eclipse caused by Earth’s shadow on the Moon.Ordinary full Moon without alignment.

7. Six months later the tilt orientation makes south face the Sun more directly. What is predicted? Which inference or prediction is best supported?The hemispheric seasonal-light contrast reverses.Both hemispheres permanently retain the prior contrast.Earth must stop rotating.A season guarantees identical daily weather.

8. Supplied case 6: model period (days)=40; cycle fraction=0.25, using the explicitly named quantities. Elapsed model days equal period in days multiplied by cycle fraction. What result follows?160 days11 days9 days10 days

9. A variant’s frequency rises over generations, but heredity and offspring differences are unmeasured. What is warranted? Which inference or prediction is best supported?The variant must improve every environment.A frequency change alone does not establish natural selection.Every frequency change proves purposeful adaptation.Inheritance and reproduction never matter.

10. Supplied case 6: trait count=42; population count=70, using the explicitly named quantities. Trait percentage equals 100 times trait count divided by total count. What result follows?60 %166.66667 %61 %59 %

11. A fossil sequence contains dated earlier and later forms with some shared structures. What can it support? Which inference or prediction is best supported?All unpreserved organisms never existed.The oldest fossil must be the direct ancestor of every later one.Dates alone identify every evolutionary mechanism.A time-constrained history comparison, without proving every missing transition.

12. A tree shows three branches from an unresolved node with no pairwise order. What follows? Which inference or prediction is best supported?The longest label proves the oldest lineage.The uncertainty proves the lineages are unrelated.The model does not resolve which pair shares the more recent divergence.The leftmost pair must be closest.

13. A surface separates older layers from younger deposits with a preserved gap. What is warranted? Which inference or prediction is best supported?The record can omit time through erosion or nondeposition.No time passed at the gap.Every event is continuously preserved.The gap fixes an exact duration without dating.

14. Supplied case 6: interval (million years)=15.4, using the explicitly named quantities. Years equal supplied million years multiplied by one million. What result follows?15400 years15400001 years15399999 years15400000 years

15. A sample’s reported age is 50±3 million years under its dating model. What should the report preserve? Which inference or prediction is best supported?The interval proves every surrounding layer has that age.Relative position replaces all dating assumptions.The estimate and its stated uncertainty rather than an exact 50.The uncertainty must be erased.

16. Two buildings face equal shaking but their modeled resistance differs. What explains a damage difference? Which inference or prediction is best supported?Damage alone identifies exact future earthquakes.Vulnerability differs while supplied hazard/exposure are held fixed.The stronger building changed the earthquake’s timing.Equal shaking guarantees equal damage.

17. The supplied vacuum model changes red light to a higher-frequency visible wave. What changes? Which inference or prediction is best supported?Speed increases solely because frequency rises.Wavelength and frequency both increase at fixed speed.The wave becomes sound automatically.Wavelength decreases while propagation speed stays the same.

18. Supplied case 6: frequency (Hz)=12; wavelength (m)=0.25, using the explicitly named quantities. Wave speed equals frequency in hertz multiplied by wavelength in meters. What result follows?4 m/s2 m/s3 m/s48 m/s

19. Light continues through a pane and bends at entry. What distinction is needed? Which inference or prediction is best supported?Transmission destroys the entering ray’s energy.Transmission describes passage; refraction describes the direction change.Passing and bending are mutually impossible.Bending proves total reflection only.

20. A receiver uses a different code table than the sender, even with unchanged bits. What is predicted? Which inference or prediction is best supported?Meaning can differ because the mapping is inconsistent.Correct bits guarantee meaning under any code.The differing table changes vacuum light speed.The sender’s table is inferred without agreement.

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