Nokea
What is the unit of force in the SI system?
- A. Newton (N)
- B. Kilogram (kg)
- C. Meter (m)
- D. Second (s)
Correct Answer: A
Rationale: The unit of force in the SI system is the Newton (N). It is defined as the amount of force required to accelerate a mass of one kilogram at a rate of one meter per second squared. In the SI system, force is measured in Newtons, not in kilograms, meters, or seconds. Choice B, Kilogram (kg), is incorrect because kilograms are units of mass, not force. Choice C, Meter (m), is incorrect because meters are units of length, not force. Choice D, Second (s), is incorrect because seconds are units of time, not force.
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How do vaccines primarily function within the body?
- A. Creating a physical barrier against pathogens
- B. Triggering an inflammatory response
- C. Developing immunological memory to a specific pathogen
- D. Activating phagocytes to engulf pathogens
Correct Answer: C
Rationale: Vaccines primarily function by stimulating the immune system to develop immunological memory to a specific pathogen. When a vaccine is administered, it exposes the immune system to a harmless version of a pathogen or a piece of it. This exposure triggers the immune response, leading to the production of antibodies and memory cells specific to that pathogen. Choice A is incorrect because vaccines do not create a physical barrier; rather, they prepare the immune system to recognize and fight specific pathogens. Choice B is incorrect as vaccines do trigger an immune response, but the primary goal is to create memory rather than inflammation. Choice D is incorrect as vaccines do not directly activate phagocytes; instead, they stimulate the immune system to generate a targeted response against a particular pathogen.
What is the process of separating a mixture based on the different boiling points of its components called?
- A. Filtration
- B. Chromatography
- C. Distillation
- D. Centrifugation
Correct Answer: C
Rationale: Distillation is the process of separating a mixture based on the different boiling points of its components. During distillation, the mixture is heated to vaporize the component with the lowest boiling point first. The vapor is then cooled and condensed back into a liquid, allowing for the collection of fractions with different boiling ranges. This technique is effective for separating components that have significantly different boiling points. Filtration (Choice A) is a method used to separate solids from liquids or gases using a filter medium. Chromatography (Choice B) is a technique used to separate components of a mixture based on their differential affinities to a stationary phase and a mobile phase. Centrifugation (Choice D) is a process of separating particles from a solution based on differences in size, shape, density, and viscosity by spinning the mixture at high speeds.
What is the energy required to break a chemical bond called?
- A. Kinetic energy
- B. Potential energy
- C. Activation energy
- D. Bond energy
Correct Answer: C
Rationale: Activation energy is the energy required to break a chemical bond and initiate a chemical reaction. It is the minimum amount of energy needed to start a chemical reaction by breaking bonds in the reactant molecules. Kinetic energy (option A) is the energy of motion and is not directly related to breaking chemical bonds. Potential energy (option B) is stored energy that can be converted into other forms of energy but is not specifically about breaking chemical bonds. Bond energy (option D) refers to the energy required to break a particular chemical bond in a molecule and is not the general term for the energy needed to break any chemical bond. Activation energy is crucial in determining the rate of a chemical reaction as it affects the probability of reactant molecules colliding with sufficient energy to surpass the energy barrier and form products.
What determines the magnitude of the frictional force acting on a book sliding across a table?
- A. Only the mass of the book
- B. Only the normal force from the table
- C. Both the mass of the book and the normal force from the table
- D. Neither the mass of the book nor the normal force from the table
Correct Answer: C
Rationale: The magnitude of the frictional force acting on the book sliding across a table is determined by both the mass of the book and the normal force from the table. Frictional force is proportional to the normal force (which is influenced by the weight of the book, i.e., its mass) and is affected by the surfaces in contact and other friction-related factors. Therefore, both the mass of the book and the normal force from the table are essential in determining the frictional force experienced by the book during its sliding motion. Choices A, B, and D are incorrect because friction is a result of the interaction between the surfaces and is influenced by both the mass of the object and the normal force acting on it.
What are the three main types of muscle tissue in the human body?
- A. Smooth, cardiac, and voluntary skeletal
- B. Smooth, skeletal, and involuntary cardiac
- C. Voluntary smooth, cardiac, and skeletal
- D. Striated, non-striated, and epithelial
Correct Answer: A
Rationale: The three main types of muscle tissue in the human body are smooth muscle (involuntary), cardiac muscle (involuntary), and voluntary skeletal muscle. Smooth muscle is found in the walls of hollow organs, cardiac muscle is found in the heart, and skeletal muscle is attached to bones and is under voluntary control. Option A correctly identifies these three main types of muscle tissue in the human body. Choice B is incorrect because it lists skeletal muscle as involuntary, which is not accurate. Choice C is incorrect because it lists voluntary smooth muscle, which does not exist as smooth muscle is involuntary. Choice D is incorrect because it uses terms like striated, non-striated, and epithelial, which are not the main types of muscle tissue but rather descriptions related to muscle characteristics and location.