How does kinetic energy change when the velocity of an object is doubled?

Correct Answer: B

Rationale: Kinetic energy is directly proportional to the square of the velocity of an object according to the kinetic energy formula (KE = 0.5 * m * v^2). When the velocity is doubled, the kinetic energy increases by a factor of 2^2 = 4. Therefore, the kinetic energy quadruples when the velocity of an object is doubled. Choice A is incorrect because halving the kinetic energy would be the result if the velocity was halved, not doubled. Choice C is incorrect because doubling the velocity would result in a fourfold increase in kinetic energy, not just a double. Choice D is incorrect because kinetic energy is directly related to the velocity of an object, so if the velocity changes, the kinetic energy changes accordingly.

Correct Answer: C

Rationale: Ductility is the property of a substance that allows it to be stretched into thin wires without breaking. It is a crucial property for materials used in wire production. Conductivity refers to the ability of a substance to conduct electricity or heat, not to be stretched into wires. Viscosity is the measure of a fluid's resistance to flow, not its ability to be stretched. Malleability is the property of a substance that allows it to be hammered or rolled into thin sheets, not stretched into wires.

Correct Answer: B

Rationale: Nucleotide: Nucleotides are the building blocks of RNA. A nucleotide consists of a nitrogenous base (adenine, guanine, cytosine, or uracil in RNA), a sugar (ribose in RNA), and a phosphate group. A) Amino acid: Amino acids are the building blocks of proteins, not RNA. C) Protein: Proteins are made up of amino acids, not nucleotides. D) Fatty acid: Fatty acids are components of lipids, not RNA.

Correct Answer: C

Rationale: A genetic disorder caused by a mutation on the X chromosome is termed a sex-linked recessive disorder (Option C). This type of disorder is more commonly seen in males due to their single X chromosome, making them more vulnerable to X-linked mutations. Females have two X chromosomes, providing a protective effect against X-linked disorders.\n- Autosomal dominant disorders (Option A) result from a mutation in one copy of a gene on non-sex chromosomes (autosomes) and are not specifically related to the X chromosome.\n- Autosomal recessive disorders (Option B) occur due to mutations in both copies of a gene on autosomes, not on the X chromosome.\n- Sex-linked dominant disorders (Option D) are rare and lead to more severe symptoms in males as they only require one copy of the mutated gene on the X chromosome to express the disorder. However, this is not the term for a genetic disorder caused by an X chromosome mutation.

Correct Answer: B

Rationale: Kinetic energy is directly proportional to the square of the velocity of an object according to the kinetic energy formula (KE = 0.5 * m * v^2). When the velocity is doubled, the kinetic energy increases by a factor of 2^2 = 4. Therefore, the kinetic energy quadruples when the velocity of an object is doubled. Choice A is incorrect because halving the kinetic energy would be the result if the velocity was halved, not doubled. Choice C is incorrect because doubling the velocity would result in a fourfold increase in kinetic energy, not just a double. Choice D is incorrect because kinetic energy is directly related to the velocity of an object, so if the velocity changes, the kinetic energy changes accordingly.

Correct Answer: C

Rationale: When a ball is thrown horizontally, its horizontal velocity remains constant throughout its motion. The horizontal distance traveled by the ball is determined by the horizontal velocity and the time taken to hit the ground. In this case, the horizontal distance is calculated as distance = velocity time. Since the horizontal velocity is 10 m/s, the horizontal distance traveled by the ball is 10 m/s time. The time taken to hit the ground is determined by the vertical motion, which is independent of the horizontal velocity. Therefore, without knowing the height of the cliff, we can still determine the horizontal distance traveled by the ball. The horizontal distance is solely dependent on the horizontal velocity and the time of flight, which are not influenced by the height of the cliff. Hence, the correct answer is 30 m. Choice A, 10 m, is incorrect as it does not consider the time of flight. Choice B, 20 m, is incorrect as it does not account for the constant horizontal velocity. Choice D, 'Cannot be determined without knowing the height of the cliff,' is incorrect because the horizontal distance can be calculated independently of the height of the cliff.

Correct Answer: B

Rationale: Protein is essential for muscle growth and repair as it provides the necessary building blocks (amino acids) for muscle tissue synthesis and repair. While vitamins and minerals are crucial for overall health, protein has a specific role in muscle development. Carbohydrates supply energy for workouts, and fats are important for general health but are less directly involved in muscle growth and repair compared to protein.

Correct Answer: B

Rationale: K-strategists are species with a low reproductive rate that invest more resources in raising fewer offspring. These species typically live in stable environments with limited resources. The main factor limiting population growth in K-strategists is the availability of resources such as food, shelter, and space. When resources are scarce, K-strategists may struggle to find enough to support their population size, leading to reduced reproductive success and population growth. While predation, competition, and disease can also impact population growth, the primary limiting factor for K-strategists is the availability of resources.

Correct Answer: C

Rationale: Friction is a force that opposes motion. When two surfaces are in contact, friction acts in the opposite direction to the motion or the potential motion between the two surfaces. It resists the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Friction hinders or prevents motion rather than promoting it. Choices A, B, and D are incorrect as they suggest that friction increases, accelerates, or creates motion, which is inaccurate. The correct definition of friction is that it opposes motion, making choice C the most appropriate option.