Which force opposes the relative motion between surfaces in contact?

Correct Answer: B

Rationale: The correct answer is B: Frictional force. Frictional force opposes the relative motion between surfaces in contact. When two surfaces are in contact and one tries to slide over the other, the frictional force resists this motion, making it harder for the surfaces to move relative to each other. Choice A, tension force, is incorrect because tension force is a force transmitted through a string, rope, cable, or wire when it is pulled tight by forces acting from opposite ends. Choice C, gravitational force, is incorrect as it is the force of attraction between two masses. Choice D, magnetic force, is incorrect as it is the force exerted between magnetic objects.

Correct Answer: B

Rationale: When a balanced force acts on an object, the net force is zero, resulting in no acceleration. This means that the object will continue to move with a constant velocity if it was already in motion or remain at rest if it was initially stationary. Choice A is incorrect because the object can also move with constant velocity. Choice C is incorrect as acceleration only occurs when an unbalanced force is applied. Choice D is incorrect as the mass of an object is not affected by the balance of forces acting on it.

Correct Answer: A

Rationale: Kinetic energy is the energy an object possesses due to its motion. The formula to calculate kinetic energy is KE = 0.5 mass velocity^2, which can also be written as KE = mass (velocity)^2. Therefore, the correct formula is Kinetic Energy = Mass Velocity. Choice B is incorrect because it represents the work formula. Choice C is incorrect as it represents the formula for work done. Choice D is incorrect as it does not accurately represent the formula for calculating kinetic energy.

Correct Answer: A

Rationale: A single gene mutation can lead to multiple phenotypes through pleiotropy, where one gene influences diverse traits or functions in an organism. This phenomenon occurs when the mutated gene affects different biochemical pathways, developmental processes, or cellular functions, resulting in a cascade of downstream effects that manifest as a variety of phenotypic outcomes. Choice B, epigenetics, involves modifications in gene expression influenced by environmental factors without altering the DNA sequence, which is not directly related to the question about single gene mutations causing multiple phenotypes. Choice C, genetic drift, refers to random changes in allele frequencies within a population, which is unrelated to the impact of a single gene mutation on multiple phenotypes. Choice D, gene regulation, focuses on controlling the timing and level of gene expression within an organism, which is not directly addressing how a single gene mutation can lead to diverse phenotypes.

Correct Answer: B

Rationale: Work is directly proportional to both force and displacement. The work done on an object is calculated by multiplying the force applied to the object by the distance the object moves in the direction of the force. Therefore, work is directly proportional to both force and displacement. Choice A is incorrect because work is not inversely proportional to displacement. Choice C is incorrect because work is not inversely proportional to force. Choice D is incorrect because work is not inversely proportional to both force and displacement.