Concept checking (56 marks)
Decide
whether the following statements are true or false, and try to rewrite the true
statements.
1.
Non-contact
force can only exist between objects that are not in contact. True / False
2.
Magnetic
force and the force of gravity are examples of non-contact forces. True / False
3.
The mass of
an astronaut on the moon is less than that on the Earth. True / False
The mass of an astronaut on the moon is
the same as that on the Earth.
4.
A force is
always needed to keep an object moving. True
/ False
A force may not be needed to keep an
object moving.
5.
When there is
no force acting on a moving object, it will eventually stop. True / False
When there is no force acting on a moving
object, it will not stop.
6.
Friction only
acts on a moving object. True
/ False
Friction not only acts on a moving
object.
7.
A hovercraft
uses water to reduce friction. True
/ False
A hovercraft uses air cushion to reduce
friction.
8.
Action and
reaction always act in opposite directions. True / False
9.
Action and
reaction always have the same size. True / False
10. A rocket produces an upward pushing force by
ejecting hot gases downward. True / False
11. When we ride on the ‘Abyss Turbo Drop’, the force
of gravity acting on us is zero at a certain moment. True
/ False
When we ride on the ‘Abyss Turbo Drop’,
the force of gravity acting on us is the same at any movement.
12. A parachute cannot work in a vacuum. True / False
13. The unit of force can be Newton or kilogram. True
/ False
The unit of force is Newton.
14. A force can start or stop a motion. True / False
15. A force can change the speed of an object. True / False
16. Force exists between two objects only when they are
in contact. True
/ False
Force exists between two objects when
they are in contact or not in contact.
17. Weight is a force. True / False
18. To start the upward motion of an object, the upward
push must be larger than the object’s weight. True / False
19. The weight of an object is measured in kilogram. True
/ False
The weight of an object is measured in
Newton.
20. Friction is useless in our daily lives. True
/ False
Friction is useful in our daily lives.
21. An object has the same mass on the Earth and on the
Moon. True / False
22. There is no gravity on the Moon. True
/ False
There is gravity on the Moon.
23. A streamlined design can reduce air friction. True / False
24. The grooves in a tyre can prevent a car from
slipping. True / False
25. A stream-lined design can reduce air friction. True / False
26. Forces always occur in pairs. True / False
27. The rocket engines must always be on in space
travel. True
/ False
The rocket engines may not be on in space
travel.
28. A rocket can move around the Earth with its engine
off. True / False
Sentence rearranging (5 marks)
Rewrite the sentence
with the following words in correct sequence.
1.
can / A
force / of
/ object /
an / change
/ the speed
A force can change the speed of an
object.
2.
can be /
Forces / a spring balance /
measured / by
Forces can be measured by a spring
balance.
3.
is /
measured / Weight
/ newtons / in
Weight is measured in Newon.
4.
lubricants /
can be / such as
/ Friction /
oil / reduced
/ by
Friction can be reduced by lubricant such
as oil.
5.
action /
always / Forces
/ pair /
reaction / occur in
/ and
Action and reaction always occur in pair
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