Nokea
Deuterium, a stable isotope of hydrogen, has a nucleus containing:
- A. A single proton
- B. A proton and a neutron
- C. Two protons and an electron
- D. Two neutrons
Correct Answer: B
Rationale: Deuterium, as an isotope of hydrogen, has an atomic number of 1 and a mass number of 2. The nucleus of deuterium contains one proton (as in all hydrogen atoms) and one neutron, totaling 2 nucleons in the nucleus. Therefore, the correct answer is that deuterium's nucleus contains a proton and a neutron. Choices A, C, and D are incorrect. Deuterium is not just a single proton (A), doesn't have two protons and an electron (C), and doesn't contain two neutrons (D). The correct composition of deuterium's nucleus is one proton and one neutron.
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Which of the following is a characteristic of unsaturated fatty acids?
- A. They are solid at room temperature.
- B. They contain only single bonds.
- C. They have a higher melting point.
- D. They contain double or triple bonds.
Correct Answer: D
Rationale: The correct answer is D. Unsaturated fatty acids are characterized by the presence of double or triple bonds in their carbon chain. These bonds introduce kinks in the chain, preventing tight packing, and resulting in a lower melting point compared to saturated fatty acids. Choice A is incorrect because unsaturated fatty acids are typically liquid at room temperature due to their kinked structure. Choice B is incorrect because unsaturated fatty acids contain double or triple bonds, not only single bonds. Choice C is incorrect as unsaturated fatty acids have a lower melting point compared to saturated fatty acids.
What is the work done by a force of 20 N acting on an object that moves 5 meters in the direction of the force?
- A. 100 Joules (J)
- B. 25 Joules (J)
- C. 4 Joules (J)
- D. Work cannot be determined without knowing the object's mass.
Correct Answer: A
Rationale: The work done is calculated using the formula: Work = Force x Distance x cos(theta), where theta is the angle between the force and the direction of motion. In this case, the force and the direction of motion are in the same direction, so cos(theta) = 1. Therefore, Work = 20 N x 5 m x 1 = 100 Joules. Since the force and distance are given and are in the same direction, the work done can be directly calculated without needing to know the object's mass. Choice A, 100 Joules, is the correct answer as calculated. Choice B and C are incorrect as they do not correspond to the correct calculation. Choice D is incorrect because knowing the object's mass is not necessary to calculate work in this scenario, as work is dependent on force, distance, and the angle between them, not mass.
Identify the opposing muscle pair.
- A. Bicep and tricep (Arm flexion and extension)
- B. Hamstring and quadriceps (Knee extension and flexion)
- C. Pectoralis major and pectoralis minor (Chest muscles)
- D. Trapezius and deltoid (Shoulder movement)
Correct Answer: A
Rationale: The correct answer is A. The bicep and tricep muscles form an antagonistic muscle pair, where one muscle contracts while the other relaxes. The bicep, located on the front of the upper arm, is responsible for arm flexion (bending the elbow), while the tricep, situated on the back of the upper arm, is responsible for arm extension (straightening the elbow). This opposing action allows for controlled movement at the elbow joint. Choice B, hamstring and quadriceps, are not opposing muscles in the context of the knee joint; the hamstring group flexes the knee, while the quadriceps group extends it. Choices C and D do not represent an opposing muscle pair related to joint movement.
A car brakes to a stop on a level road. Which of the following forces does NOT do work on the car?
- A. The braking force applied by the wheels
- B. The normal force from the road
- C. The gravitational force on the car
- D. The friction force between the tires and the road
Correct Answer: B
Rationale: The normal force from the road does not do work on the car because it is perpendicular to the direction of motion. Work is defined as force applied in the direction of motion, so the normal force, which acts perpendicular to the motion of the car, does not contribute to the work done on the car. The braking force applied by the wheels, the gravitational force on the car, and the friction force between the tires and the road all act in the direction of motion and contribute to the work done on the car. In this scenario, the normal force is supporting the weight of the car and keeping it from sinking into the road, but it does not transfer energy to the car as it moves.
Which of the following organs is responsible for the mechanical breakdown of food into smaller pieces?
- A. Esophagus
- B. Stomach
- C. Small intestine
- D. Mouth
Correct Answer: D
Rationale: The correct answer is D: Mouth. The mouth is responsible for the mechanical breakdown of food through chewing and mixing with saliva. This process is essential for breaking down food into smaller, more digestible pieces before swallowing. The esophagus (choice A) is a muscular tube that transports food from the mouth to the stomach and does not participate in the mechanical breakdown of food. The stomach (choice B) primarily functions to further break down food using acids and enzymes, rather than mechanical means. The small intestine (choice C) is responsible for absorbing nutrients from the digested food, not for the mechanical breakdown of food.