1.
How can one define dry friction?
Correct Answer
A. It's a force that opposes the relative lateral motion of 2 solid surfaces in contact
Explanation
Dry friction can be defined as a force that opposes the relative lateral motion of two solid surfaces in contact. This means that when two surfaces are in contact and there is an attempt to slide or move them laterally, dry friction acts in the opposite direction to resist this motion. It is important to note that dry friction occurs between solid surfaces and does not involve any lubrication or fluid medium.
2.
How many other frictions are there apart from dry friction?
Correct Answer
A. 4
Explanation
There are four other types of frictions apart from dry friction. These include static friction, which occurs when two objects are not moving relative to each other, but there is a force preventing their movement. Kinetic friction is the resistance experienced when two objects are sliding against each other. Rolling friction occurs when an object rolls on a surface, and fluid friction is the resistance encountered by an object moving through a fluid, such as air or water.
3.
What happens when surfaces in contact move relative to each other?
Correct Answer
A. The friction between the 2 surfaces converts kinetic energy into thermal energy
Explanation
When surfaces in contact move relative to each other, the friction between them converts kinetic energy into thermal energy.
4.
What causes dry friction?
Correct Answer
A. It's a combination of inter-surface adhesion, surface roughness, surface deformation, and surface contamination
Explanation
Dry friction is caused by a combination of factors including inter-surface adhesion, surface roughness, surface deformation, and surface contamination. Inter-surface adhesion refers to the molecular attraction between the two surfaces in contact. Surface roughness refers to the irregularities or unevenness on the surfaces that create friction. Surface deformation occurs when the surfaces are pressed together, causing them to conform to each other and increase friction. Surface contamination refers to the presence of foreign substances on the surfaces that can affect the frictional behavior. The combination of these factors contributes to the occurrence of dry friction.
5.
What's the nature friction?
Correct Answer
D. It's a non-conservative force
Explanation
Friction is considered a non-conservative force because it dissipates energy in the form of heat and sound as two objects slide or rub against each other. Unlike conservative forces, which conserve mechanical energy, friction converts mechanical energy into other forms, leading to a loss of energy in the system.
6.
What is the meaning of non-conservative force?
Correct Answer
A. It's when the total work done in moving a particle between 2 points is not dependent on the taken path
Explanation
A non-conservative force is a force that does not conserve mechanical energy. In other words, the total work done by a non-conservative force in moving a particle between two points is not dependent on the path taken. This means that the work done by the force will be the same regardless of the specific route taken between the two points.
7.
What does it mean when friction between 2 surfaces converts kinetic energy into thermal energy?
Correct Answer
A. It converts work to heat
Explanation
When there is friction between two surfaces, kinetic energy is converted into thermal energy. This means that the energy associated with the motion of the objects is transformed into heat energy. Friction causes the surfaces to rub against each other, resulting in the generation of heat. This heat energy is a form of thermal energy and represents the conversion of work, or the energy of motion, into heat.
8.
What is mechanical energy?
Correct Answer
C. It's the sum of potential energy and kinetic energy
Explanation
Mechanical energy refers to the total energy possessed by an object due to its motion or position. It is the combination of potential energy, which is the energy stored in an object based on its position or configuration, and kinetic energy, which is the energy possessed by an object due to its motion. Therefore, the correct answer states that mechanical energy is the sum of potential energy and kinetic energy.
9.
Why is friction important to cars?
Correct Answer
C. Because cars rely on friction for acceleration, deceleration, and changing direction
Explanation
Friction is important to cars because it allows them to accelerate, decelerate, and change direction. When a car's tires grip the road surface, friction is created, allowing the car to move forward or backward. This friction also helps the car slow down and come to a stop when the brakes are applied. Additionally, friction between the tires and the road allows the car to change direction by providing the necessary grip and traction. Without friction, cars would not be able to move, stop, or maneuver effectively.
10.
What is the opposite of dry friction?
Correct Answer
A. Fluid friction
Explanation
The opposite of dry friction is fluid friction. Dry friction occurs when two solid surfaces come into contact and resist each other's motion, while fluid friction occurs when an object moves through a fluid medium, such as air or water. In fluid friction, the fluid molecules create resistance against the object's motion, making it harder for the object to move. This is in contrast to dry friction, where the resistance is caused by the roughness and interlocking of the solid surfaces.