Explanation

• Non-luminous objects do not emit light of their own, but they can reflect, transmit, or absorb light from other sources.
• Examples: Moon, furniture in the room, books, clothes, trees, planets, paper and most solid objects.

Explanation

• A nail cutter is an example of a Second-class lever.
• Where the load (the nail) is located between the effort (the hand) and the fulcrum (the pivot point of the cutter).

Explanation

According to the positions of effort, fulcrum, and load, levers are divided into three kinds:

1. First kind of lever: The fulcrum is located between the effort and the load. Examples: See-saws, crowbars, hammer claws, scissors, pliers and boat oars.
2. Second kind of lever: The load is located between the effort and the fulcrum. Examples: Bottle opener, wheelbarrow, nut cracker, nail clippers, nail cutter, paper cutter and door.
3. Third kind of lever: The effort is located between the fulcrum and the load. Examples: Broom, tongs, human arm, stapler, fishing rod and tweezers.

Explanation

• Mass is a measure of the amount of matter in an object, and it remains constant regardless of where you are in the universe.
• Your mass on Earth is the same as your mass on the Moon, because you are still made up of the same amount of matter.
• However, your weight (the force exerted on you by gravity) would be different on the Moon, because the Moon has a much weaker gravitational field than Earth.

Explanation

• Gravity is the force that pulls objects towards the Earth.
• Keeping us and everything else on the ground.

Explanation

• Swimmers make their bodies streamlined to reduce friction underwater.
• It allowing them to move more efficiently and quickly through the water.

Explanation

• Friction forces between the air and a moving object cause resistance.
• Which slows down the object and converts some of its kinetic energy into heat.

Explanation

• Grease is a lubricant that can be used to reduce friction between moving parts of machines.
• It helps to reduce wear and tear, prevent overheating, and allow parts to move smoothly.

Explanation

• Increasing the weight is not a way to reduce friction.

Ways to reduce friction:

• Smoothing and polishing surfaces
• Reducing contact area
• Using oil and lubricants
• Using ball bearings and rollers

Explanation

• Fasteners (such as nuts and bolts) actually benefit from friction, as it helps keep them in place.

Disadvantages of friction:

• Energy loss: Friction converts useful energy into non-usable forms like heat.
• Wear and tear: Friction causes moving parts to wear out and deteriorate.
• Speed limit: Friction limits the maximum speed of automobiles.