1. A major earthquake occurs along the boundary of two tectonic plates. The seismic focus is located beneath the Earth's surface. What is the significance of the epicentre in understanding the impact of the earthquake?
a) The epicentre determines the depth of the earthquake focus.
b) The epicentre indicates the first area to experience ground shaking.
c) The epicentre marks the point where tectonic plates collide.
d) The epicentre determines the magnitude of the earthquake.
Answer: b) The epicentre of an earthquake is the point on the Earth's surface directly above the seismic focus, which is the actual location where the earthquake originates within the Earth's crust. When an earthquake occurs, the seismic waves radiate outward from the focus in all directions and reach the Earth's surface at the epicentre first. This is why the epicentre is the first area to experience ground shaking and the initial impact of the earthquake's effects. As the seismic waves continue to propagate, they affect areas farther from the epicentre, causing a ripple effect of ground shaking. Therefore, the epicentre's location is crucial in understanding where the earthquake's impact is most significant initially.
2. When a plastic comb is rubbed against dry hair, the comb becomes negatively charged. What is the reason behind this charge transfer?
a) Hair loses electrons and becomes positively charged.
b) Hair gains protons and becomes positively charged.
c) Hair gains electrons and becomes negatively charged.
d) Hair loses protons and becomes negatively charged.
Answer: a) When a plastic comb is rubbed against dry hair, the rubbing process causes the transfer of electrons between the two materials. The plastic comb has a higher affinity for electrons compared to dry hair. As a result, when the two materials come into contact and are rubbed together, electrons are transferred from the hair to the comb. This leads to an excess of electrons on the comb, giving it a negative charge, while the hair loses electrons and becomes positively charged. This phenomenon is an example of static charge generation through the process of friction.
3. An earthquake with a magnitude of 7 on the Richter scale releases how much more energy compared to an earthquake with a magnitude of 5?
a) 2 times more energy.
b) 10 times more energy.
c) 100 times more energy.
d) 1000 times more energy.
Answer: d) The Richter scale is a logarithmic scale used to measure the magnitude of earthquakes. For each whole number increase on the Richter scale, there is a tenfold increase in the amplitude of seismic waves and approximately 31.6 times more energy is released.
Given that an earthquake with a magnitude of 7 is 2 whole numbers higher than an earthquake with a magnitude of 5:
Magnitude 7 earthquake: (31.6)2 times more energy than a magnitude 5 earthquake.
Therefore, an earthquake with a magnitude of 7 releases 1000 times more energy compared to an earthquake with a magnitude of 5.
4. Imagine you are camping in an open field during a thunderstorm. Which of the following actions would be the safest based on lightning safety guidelines?
a) Stay near a tall metal pole to minimise the risk of being struck by lightning.
b) Lie flat on the ground to reduce your height and exposure to lightning
c) Find shelter under a small tree to shield yourself from the rain and wind.
d) Seek refuge in a car, bus, or sturdy building to reduce the risk of being struck by lightning.
Answer: d) During a thunderstorm, seeking shelter in a car, bus, or sturdy building is the safest option as these structures provide a safer pathway for lightning to travel through, reducing the risk of being struck. Open fields, tall metal poles, and trees are not safe options as they increase the risk of being struck by lightning due to their height and exposure to the open sky. Lying flat on the ground does not provide adequate protection from lightning.
5. A gold-leaf electroscope is used to determine the nature of a charged object. How will the leaves of the electroscope behave when a positively charged object is brought close to it?
a) The leaves will repel each other.
b) The leaves will remain unchanged.
c) The leaves will attract each other.
d) The leaves will deflect outward.
Answer: c) When a positively charged object is brought close to the gold-leaf electroscope, the leaves of the electroscope will also become positively charged due to induction. Since like charges repel each other, the leaves will repel each other and move apart, demonstrating a deflection outward. This behaviour of the leaves indicates that the electroscope itself has acquired a positive charge, leading to the observed repulsion between the leaves.
