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- What is the formula for
speed? (lesson 31a)
- A girl runs 100m in 20
seconds. What is her average speed? (31a)
- If 2 forces are balanced,
they must be e---- and o-------. (31a)
- A boy pushes a box with a
force of 100N. There is a friction force of 80N. What is the resultant
force? (31a)
- If the forces on an
object are balanced, it will either stay -----, or if moving it will carry
on moving at a steady ----- in a -------- line. (31a)
- What is the formula for
calculating a moment? (31b)
- State the principle of
moments. (31b)
- What is the name of the
force that the Earth exerts on you? (31c,f,g)
- What is the centre of
gravity? (31c)
- State the formula for
pressure. (31d)
- A box weighs 500 newtons.
The area touching the floor is 100cm3. What is the pressure?
(31d)
- Name the 9 planets in
order. (31h)
- How long does it take the
Earth to i) spin round once? ii) go once round the Sun? (31h)
- a) In ------, our part of
the Earth is tilted towards the Sun. b) At that time of the year, the Sun is
------ in the sky. (31h)
- What is the difference in
the way that we get light a) from stars and b) from planets? (31h)
ANSWERS
- Average speed = distance
travelled (in metres)/time taken (in seconds).
- 5m/s (5 metres per
second).
- Equal and opposite.
- 20N.
- Still, speed, straight.
- Moment of a force = force
(in N) X distance from pivot (in metres).
- When an object is
balanced (it is 'in equilibrium') then: the anti-clockwise moments = the
clockwise moments.
- Weight (or the force of
gravity, or gravitational force, or gravitational attraction).
- It is the point where all
the weight of the object appears to act.
- pressure = force (in
N)/area (in m2 or cm2).
- 5 N/cm2 (5
newtons per square centimetre).
- Mercury, Venus, Earth,
Mars, Jupiter, Saturn, Uranus, Neptune, Pluto.
- i) 24 hours (1 day). ii)
365¼ days (1 year).
- a) Summer. b) higher.
- a) stars (including the
Sun) are light sources - they radiate light. b) planets (and moons) reflect
light.
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