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Questions and Answers
What is usually greater when something moves on a rough surface compared to a smooth surface?
Why does car A go further and faster than car B?
What is one of the benefits of friction?
What problem is caused by friction in machines?
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What is a way to reduce the unwanted effects of friction?
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What is the minimum force needed to make the block start moving?
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What is the effect of friction on the eraser?
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Why does the train go slow down?
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What is one of the problems caused by friction?
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What is one of the benefits of friction in daily life?
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Study Notes
Light and Shadow
- A shadow is formed when the path of light is blocked by an object.
- Transparent materials, like clear glass, do not form shadows when light sources are blocked, while opaque materials, like boxes, do form shadows.
- The size, length, and position of a shadow can change depending on the position of the object and light source.
- Moving the object closer to or further from the light source affects the size of the shadow.
- Materials can be classified as transparent, translucent, or opaque based on how they interact with light.
The Earth and The Moon
- The Earth is a spherical object with a rocky crust.
- The Moon is a natural satellite of the Earth, taking 29 days to orbit it.
- The Moon has craters formed by space rocks hitting its surface.
- The Sun is a star at the center of our Solar System, providing light to the Earth and Moon.
- Every object with mass has gravity, pulling everything towards its center.
- Moon phases change as the Moon orbits the Earth, with different amounts of the light and dark sides visible from Earth.
- The Moon's phases appear differently from the northern and southern hemispheres.
Mixture and Filtration
- Matter has mass and can be in solid, liquid, or gas states.
- Solids have a fixed shape and volume, while liquids take the shape of their container and have a fixed volume.
- Gases have no fixed shape or volume and can flow freely.
- A mixture is when two or more substances are physically combined but not chemically combined, and can be separated again.
- Examples of mixtures include sand and iron, flour and paper, and rice and steel nails.
- Soluble substances dissolve in a liquid, while insoluble substances do not.
- Filtration is a process that makes a substance more pure or clean.
Force and Magnet
- Force is a push or pull that creates motion, makes things change direction or shape, and can be measured in newtons (N).
- Forces can be used to make things move, stop, or change direction.
- Friction is a force that opposes motion when two surfaces are in contact, making things slow down and stop.
- The type of surface affects the amount of friction, with rough surfaces having more friction than smooth surfaces.
- Friction has benefits, such as enabling us to hold on to things and walk without slipping, but also causes problems like wear and tear.
- We can reduce the unwanted effects of friction by applying oil to moving parts or using smooth surfaces.
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Description
Assessment quiz on the concept of light and shadow for Grade 3 students, covering the formation of shadows and the path of light.
