Science 6 Trinitas Quiz Bee Reviewer Unit 3

How can we reduce frictional force?

• Streamlining

• Heavy swim wear or clothing

• Moving the opposite way

• Cannot be reduced

Answer explanation

Streamlining refers to the process of designing objects to minimize resistance to motion through a fluid medium, such as air or water. By shaping an object in a streamlined manner, it can reduce the frictional force experienced as it moves through the fluid. This principle is commonly utilized in various fields, including aerodynamics for vehicles and hydrodynamics for watercraft, to decrease drag and improve efficiency.

What form of energy is associated with vibrating mechanical waves moving through substances and objects?

• Heat energy

• Chemical energy

• Sound energy

• Mechanical energy

The lever is a simple machine. Which of the following is true about levers?

• The fulcrum is the triangle in the middle of the lever.

• The load is the force that allows the lever to move.

• The effort is the object being lifted.

• The position of the fulcrum in the middle of the arm is fixed.

Answer explanation

In a lever, the fulcrum is the pivot point around which the lever rotates. The load is the object being moved or lifted by the lever, and the effort is the force applied to the lever to move the load. The position of the fulcrum can vary depending on the type of lever, but in a simple lever, the fulcrum is typically fixed. The fulcrum is not typically a physical shape like a triangle.

Which of the following statements is true about mass?

• It is relative to the object's location.

• It is measured as the gravitational pull of Earth on an object.

• It is the total amount of matter an object contains.

• It increases as the distance between Earth and the object decreases.

Answer explanation

Mass is indeed a measure of the total amount of matter present in an object and remains constant regardless of the object's location or the gravitational force acting upon it.

We need energy in order to work. Which form of energy is it?

• Heat energy

• Sound energy

• Chemical energy

• Mechanical energy

Answer explanation

Chemical energy is stored within the bonds of atoms and molecules and can be released through chemical reactions, such as those that occur in our bodies when we metabolize food for energy. This energy can then be used to perform various forms of work.

What is the weight of an object if its mass is 2500g?

• 24.5N

• 255.1N

• 24500N

• 0.255N

Answer explanation

2500g=2500×10−3kg=2.5kg

Now, we can calculate the weight:

Weight=2.5 kg×9.81 m/s²=24.5 N

What simple machine similar to a lever is able to move in a 360-degree motion?

• Pulley

• Wheel and axle

• Screw

• Wedge

Answer explanation

A wheel and axle is a simple machine that consists of a wheel attached to a smaller axle, allowing rotational motion around a central axis. This setup enables objects to move in a circular motion, providing versatility similar to a lever but in a rotational manner.

The janitor has just finished mopping the floor. He left a sign that says, “Wet Floor.” Why did he leave this warning sign?

• He does not want the floor to get dirty again.

• He wants to warn people of the risk of accident due to lessened static friction on the floor.

• He wants to warn people of the risk of accident due to lessened kinetic friction on the floor.

• He does not want his work interrupted.

Answer explanation

When a floor is wet, it becomes slippery due to the reduction in static friction between the floor surface and footwear. This increases the risk of slipping and falling accidents. Therefore, the janitor uses the sign to warn people about the potential hazard and encourage caution when walking on the wet floor.

How do hot air balloons overcome gravity?

• They are pumped with helium gas to make them lighter than their surroundings.

• The heat inside the balloon is lowered.

• They are maneuvered to achieve the minimum amount of speed required to overcome gravitational pull.

• The inside of the balloon is kept warm.

Answer explanation

Hot air balloons overcome gravity primarily through the principle of buoyancy, which is governed by Archimedes' principle.

Hot air balloons work by heating the air inside the balloon envelope, making it less dense than the surrounding cooler air. This temperature difference creates buoyant force, causing the balloon to rise. By keeping the air inside the balloon warm, it becomes lighter than the surrounding air, allowing the balloon to float upwards. This process allows hot air balloons to overcome gravity and achieve flight.

Which type of force is perpendicular to a surface?

• Internal force

• Gravitational force

• Air resistance

• Normal force

Answer explanation

The normal force is the force exerted by a surface to support the weight of an object resting on it. It acts perpendicular to the surface and prevents objects from passing through the surface.

For example, when you place an object on a table, the table exerts a normal force upward on the object to balance the force of gravity pulling the object downward.