Space and gravity, Year 8: more practice：全部卡片
整套按顺序列出——孩子看到之前，您可以先通读一遍。
- At new Moon, why can we not see the Moon?
Its lit half faces away from the Earth
提示The Moon is still there; think about which side the Sun lights.
为什么At new Moon, the Moon is between the Earth and the Sun, so the sunlit half faces away from us.
- At full Moon, why does the Moon look like a complete bright circle?
The whole of its lit half faces the Earth
提示Think about where the Moon is in its orbit.
为什么At full Moon, the Moon is on the far side of the Earth from the Sun, so we look at the whole sunlit half.
- About how long is it from one full Moon to the next?
About a month (29.5 days)
提示Count the cycle of phases on a calendar.
为什么The cycle of phases takes about 29.5 days.
- For a lunar eclipse, which body is between the other two?
The Earth
提示The body we live on blocks the Sun's light from reaching the Moon.
为什么In a lunar eclipse the Sun, Earth and Moon are in a line with the Earth in the middle. The Moon is in the Earth's shadow.
- Which instrument measures mass: a balance or a newtonmeter?
A balance
提示One measures kilograms.
为什么A balance compares masses and gives kg. A newtonmeter measures a force, weight, in newtons.
- An astronaut weighs less on the Moon than on Earth. Why?
The Moon's gravity is weaker
提示Weight depends on the pull of the body you stand on.
为什么The Moon is smaller than the Earth, so its gravitational field strength is lower, so the same mass is pulled less. Mass is unchanged.
- Weight is a force. In which direction does it act on an object on Earth?
Towards the centre of the Earth
提示Which way would an object fall?
为什么Weight is the pull of gravity, so it acts downwards towards the centre of the Earth.
- On Earth, g = 10 N/kg. What is the weight of an 8 kg object in newtons? (number only)
80
提示W = m × g.
为什么8 × 10 = 80 N.
- On the Moon g = 1.6 N/kg. A rock has a mass of 50 kg. What is its weight there in newtons? (number only)
80
提示W = m × g.
为什么50 × 1.6 = 80 N. On Earth the same rock weighs about 500 N.
- A box weighs 240 N where g = 10 N/kg. What is its mass in kilograms? (number only)
24
提示Rearrange W = m × g.
为什么m = W ÷ g = 240 ÷ 10 = 24 kg.
1★ KS3-PHYS-SPA-0038
2★ KS3-PHYS-SPA-0039
3★ KS3-PHYS-SPA-0040
4★ KS3-PHYS-SPA-0041
5★ KS3-PHYS-SPA-0042
6★ KS3-PHYS-SPA-0043
7★ KS3-PHYS-SPA-0044
8★ KS3-PHYS-SPA-0045
9★ KS3-PHYS-SPA-0046
10★ KS3-PHYS-SPA-0047