Question 11:
Photograph 3 shows a hovercraft which can move on land or on the surface of water swiftly because of the support from a layer of air trapped under the hovercraft . Th e hovercraft of mass of 25 000 kg starts from rest and its engine produces a thrust, F of 22 000 N.
(a) Determine the initial acceleration of the hovercraft if there is no friction at that instant.
(b) What is the function of the layer of air trapped under the hovercraft?
Answer:
(a)
$$ \begin{aligned} & F=m a \\ & 22000=25000 a \\ & \text { Initial acceleration of hovercraft, } a=0.88 \mathrm{~m} \mathrm{~s}^{-2} \end{aligned} $$
(b) The layer of air trapped under the hovercraft will reduce friction between the base of the hovercraft and the water surface.
As such, the hovercraft can move more quickly.
Photograph 3 shows a hovercraft which can move on land or on the surface of water swiftly because of the support from a layer of air trapped under the hovercraft . Th e hovercraft of mass of 25 000 kg starts from rest and its engine produces a thrust, F of 22 000 N.
(a) Determine the initial acceleration of the hovercraft if there is no friction at that instant.
(b) What is the function of the layer of air trapped under the hovercraft?
Answer:
(a)
$$ \begin{aligned} & F=m a \\ & 22000=25000 a \\ & \text { Initial acceleration of hovercraft, } a=0.88 \mathrm{~m} \mathrm{~s}^{-2} \end{aligned} $$
(b) The layer of air trapped under the hovercraft will reduce friction between the base of the hovercraft and the water surface.
As such, the hovercraft can move more quickly.
Question 12:
Kok Chew and Zulkefli wish to determine Earth’s gravitational acceleration. They plan to release a table tennis ball from the third level of their school building. Discuss the suitability of the table tennis ball in this experiment.
Answer:
– Table tennis ball is not suitable to be used in this experiment.
– Table tennis ball is very light.
– Motion of table tennis ball is easily influenced by air resistance.
– Therefore, table tennis ball will not fall under free fall condition.
Kok Chew and Zulkefli wish to determine Earth’s gravitational acceleration. They plan to release a table tennis ball from the third level of their school building. Discuss the suitability of the table tennis ball in this experiment.
Answer:
– Table tennis ball is not suitable to be used in this experiment.
– Table tennis ball is very light.
– Motion of table tennis ball is easily influenced by air resistance.
– Therefore, table tennis ball will not fall under free fall condition.
Question 13:
Assume that you are an engineer who is assigned to invent a model of fast train in Malaysia. Th is train is required to travel at high speeds using levitation above the railway.
Draw your model of the fast train and list its properties by taking into consideration its shape, materials, mechanism and safety aspects.
Answer:
– Sketch based on pupil’s creativity.
– Shape of fast train should be streamlined, especially its front part has to be pointed and curved so that it has an aerodynamic shape to reduce air resistance.
– The body of the train must be made from a material of small density so that its overall mass is light and can produce a high acceleration for the same thrust of the engine.
(F = ma, for the same F, when m is small, then a is large).
– An electromagnetic system which produces the same magnetic poles between the platform and the bottom of the fast train to levitate the train above the platform.
– The train needs to be equipped with safety belts and head rests to avoid or reduce injuries due to accident.
– Fuel used by the train should be environmentally friendly. For example, electrical energy that is generated from renewable energy.
Assume that you are an engineer who is assigned to invent a model of fast train in Malaysia. Th is train is required to travel at high speeds using levitation above the railway.
Draw your model of the fast train and list its properties by taking into consideration its shape, materials, mechanism and safety aspects.
Answer:
– Sketch based on pupil’s creativity.
– Shape of fast train should be streamlined, especially its front part has to be pointed and curved so that it has an aerodynamic shape to reduce air resistance.
– The body of the train must be made from a material of small density so that its overall mass is light and can produce a high acceleration for the same thrust of the engine.
(F = ma, for the same F, when m is small, then a is large).
– An electromagnetic system which produces the same magnetic poles between the platform and the bottom of the fast train to levitate the train above the platform.
– The train needs to be equipped with safety belts and head rests to avoid or reduce injuries due to accident.
– Fuel used by the train should be environmentally friendly. For example, electrical energy that is generated from renewable energy.