UPCAT General Science (Extended) — Machines, Energy & Energy ResourcesFlash Cards

What is a lever and how does it make work easier?

A lever is a rigid object that pivots around a fulcrum. When force is applied at one end, it causes the object to pivot, which increases the force exerted at another point along the lever. This mechanical advantage makes lifting heavy objects easier by distributing the effort over a greater distance.

A crowbar is used to lift a heavy rock. If you apply 100N of force at the end of a 1-meter crowbar, and the fulcrum is 10cm from the rock, what is the mechanical advantage?

Mechanical Advantage = Length of effort arm / Length of load arm = 90cm / 10cm = 9. This means the crowbar multiplies your 100N force by 9, giving you 900N of force to lift the rock.

Name the six types of simple machines and give one example of each.

1. Lever (crowbar), 2. Wheel and axle (bicycle wheel), 3. Inclined plane (ramp), 4. Wedge (knife), 5. Screw (bolt), 6. Pulley (flagpole rope system). Each reduces the effort needed to perform work by changing the direction or magnitude of applied force.

Why is it easier to walk up a long winding path to the top of a mountain rather than climbing straight up?

The winding path acts as an inclined plane. It allows you to apply the same total work over a longer distance, reducing the force needed at any given moment. While you walk farther, each step requires less effort than climbing vertically.

What is the difference between kinetic and potential energy?

Kinetic energy is the energy of motion - any moving object has kinetic energy. Potential energy is stored energy due to position or condition - like a book on a shelf or a compressed spring. Mechanical energy is the sum of both kinetic and potential energy.

A 2kg ball is dropped from a height of 10 meters. What happens to its energy as it falls?

Initially, the ball has maximum potential energy (PE = mgh = 2×10×10 = 200J) and zero kinetic energy. As it falls, potential energy converts to kinetic energy. Just before hitting the ground, it has maximum kinetic energy (200J) and zero potential energy.

What type of energy transformation occurs in a battery-powered flashlight?

Chemical energy (in the battery) → Electric energy (current flowing through circuits) → Electromagnetic energy (light from the bulb) + Thermal energy (heat from the bulb). This demonstrates the Law of Conservation of Energy - energy changes form but is never destroyed.

Why does a metal spoon get hot when left in boiling soup?

Heat transfers from the hot soup to the metal spoon through conduction. The fast-moving molecules in the hot soup collide with the slower-moving molecules in the cooler spoon, transferring energy and increasing the spoon's temperature. Metals are good conductors of heat.

How do sea breezes form during the day?

Land heats up faster than water during the day. Hot air above the land rises (convection), creating low pressure. Cooler air from above the sea moves in to replace it, creating a sea breeze. This is convection - heat transfer through the movement of fluids (air).

How does the Sun warm the Earth across the vacuum of space?

Through radiation - the transfer of heat that doesn't require a medium. The Sun emits electromagnetic radiation (including infrared waves) that travels through empty space at the speed of light and warms Earth when absorbed by its surface.

What makes solar energy a renewable resource?

Solar energy is renewable because the Sun continuously produces energy through nuclear fusion and will do so for billions of years. The energy we use doesn't deplete the Sun's energy supply at any measurable rate, making it essentially limitless for human purposes.

Why is hydroelectric power the most widely used renewable energy source?

Hydroelectric power is reliable, efficient, and can be easily controlled. Unlike solar or wind power, water flow can be regulated through dams, providing consistent electricity generation. It converts the kinetic energy of flowing water directly into electrical energy through turbines.

How is geothermal energy generated and used?

Geothermal energy comes from the Earth's internal heat, caused by radioactive decay and residual heat from the planet's formation. This heat creates hot water and steam underground, which can be pumped to the surface to drive turbines for electricity or used directly for heating.

What are fossil fuels and why are they called 'fossil' fuels?

Fossil fuels (coal, petroleum, natural gas) are energy-rich substances formed from the remains of ancient plants, algae, and plankton that lived 300 million years ago. They're called 'fossil' fuels because they formed from fossilized organic matter subjected to extreme heat and pressure over millions of years.

Arrange these coal types from lowest to highest energy content: anthracite, lignite, bituminous, peat.

From lowest to highest energy content: Peat → Lignite → Bituminous → Anthracite. This order reflects increasing carbonization and coalification - the longer coal is buried under pressure and heat, the more carbon it contains and the more energy it provides when burned.

Why is petroleum found mostly in ocean basins and former sea floors?

Petroleum forms from the remains of dead marine organisms (algae, plankton) that accumulated on ocean floors millions of years ago. These organic-rich sediments were buried, heated, and pressurized over time, converting into oil that became trapped in underground rock formations.

How does nuclear fission generate electricity in a power plant?

Nuclear fission splits uranium atoms, releasing enormous amounts of heat energy. This heat boils water to create steam, which drives turbines connected to generators that produce electricity. The process is controlled using control rods that absorb neutrons to regulate the reaction rate.

What is the Law of Conservation of Energy?

Energy cannot be created or destroyed; it can only be transformed from one form to another. The total amount of energy in a closed system remains constant. For example, when you eat food (chemical energy), your body converts it to kinetic energy (movement) and thermal energy (body heat).

A wind turbine converts kinetic energy to electrical energy. What energy transformations occur in this process?

Wind (moving air) has kinetic energy → Turbine blades capture this kinetic energy and rotate → Rotational mechanical energy turns a generator → Generator converts mechanical energy to electrical energy. Some energy is also converted to heat due to friction.

Why can biomass be both renewable and non-renewable?

Biomass is renewable when plants/organic matter are regrown faster than they're consumed (sustainable harvesting). It becomes non-renewable when we use it faster than it can be replenished, like overharvesting forests or using fossil biomass that took millions of years to form.