1. Which question should be explored using a controlled experiment?
A. Which type of pesticide is most effective for beetles in the Midwest? Correct
B. Do elephants maintain consistent social roles within herds?
C. How do solar flares affect plant growth near the equator?
D. What is the rate at which the universe is expanding?
Explanation
A controlled experiment works best for testing cause-and-effect where one variable can be changed while keeping everything else the same. Testing different pesticides on beetles can be done in a lab or controlled field with identical conditions (same temperature, same number of beetles, same environment) to measure effectiveness fairly. Studying elephant social roles requires long-term wild observation, not a manipulable experiment—elephant behavior cannot be ethically or practically controlled. Solar flares are unpredictable natural space events; their timing and strength cannot be controlled for an experiment. Measuring the universe's expansion relies on distant astronomical observations over vast scales and cannot be replicated in a lab.
2. What is a real-world example of force being applied?
A. A fully charged battery enables a flashlight to operate.
B. A cup of water freezes after being placed in a freezer.
C. A person lifts a box from the floor onto a table. Correct
D. A box slides at a constant speed on a frictionless surface.
Explanation
Force is a push or pull on an object. Lifting a box involves applying an upward push against gravity to move it—this directly shows force in action. A charged battery provides electrical energy, not a physical push or pull. Freezing is a temperature-driven phase change, not a push or pull. A box moving at constant speed on a frictionless surface has zero net force (Newton's first law)—no unbalanced force is applied.
3. Which statement represents a general characteristic of metalloids?
A. They are poor conductors of electricity.
B. They are used for electrical wires.
C. They are both malleable and ductile.
D. They have intermediate electrical conductivity. Correct
Explanation
Metalloids (silicon, boron, arsenic) have properties between metals and nonmetals—they conduct electricity better than nonmetals but worse than metals, making them useful as semiconductors. Poor conduction describes nonmetals (insulators). Good conductors like copper (metals) are used for wires. Being malleable and ductile are typical metal properties.
4. One person pushes on a motionless box in the right direction with a force of 15 N. Another person pushes on the box in the left direction with a force of 5 N. Assuming that the static friction force is negligible, what is the result?
A. The box remains still.
B. The box moves upward.
C. The box moves to the left.
D. The box moves to the right. Correct
Explanation
Forces in opposite directions subtract: net force = 15 N right – 5 N left = 10 N right. With negligible static friction and a net unbalanced force, the box accelerates right (Newton's second law). A net force exists, so the box cannot stay still. No vertical forces are applied—both pushes are horizontal. The larger force is rightward, producing net force right.
5. A runner maintains a constant pace down the final straightaway. How are speed and velocity affected?
A. Both velocity and speed change.
B. Speed changes, but velocity does not.
C. Neither speed nor velocity changes. Correct
D. Velocity changes, but speed does not.
Explanation
The runner moves straight at constant pace—speed (magnitude) stays constant, and direction stays constant, so velocity (speed + direction) also remains unchanged. Nothing about motion is changing on a straight path. Speed is constant. Direction does not change on a straightaway.