How everyday things works with science

Question 1

Why does a car's seat belt help protect a passenger during sudden braking?

Think about what your body tends to do when the moving car suddenly slows down.

It completely removes the passenger's inertia It makes the passenger weightless It prevents the car from slowing down It restrains the passenger as inertia tends to keep the body moving forward

Question 2

Why does a black car surface often become hotter in sunlight than a similar white surface?

Consider how differently dark and light surfaces interact with incoming visible radiation.

Black surfaces produce their own sunlight Dark surfaces generally absorb more incoming solar radiation Gravity is stronger on dark-colored objects White surfaces contain permanently frozen material

Question 3

Why are the conducting parts of electrical wires covered with materials such as plastic or rubber?

The outer layer should resist the flow of electric current.

They are electrical insulators that help prevent unintended contact with current They convert electrical energy entirely into sound They increase the amount of electricity produced by the wire They make electricity visible to the human eye

Question 4

Why does a microwave oven heat many foods efficiently?

Think about how electromagnetic waves interact with molecules in food.

Microwaves cause certain molecules, especially water molecules, to respond to an alternating electric field and generate heat Microwaves fill the food with tiny flames Microwaves stop all molecular motion inside the food The oven removes every water molecule before heating begins

Question 5

Why does a metal spoon often feel colder than a wooden spoon in the same room?

Both objects may have the same temperature, but they transfer heat differently.

Metal absorbs coldness from the surrounding air Metal always has a lower room temperature than wood Metal conducts heat away from your hand faster than wood Wood produces heat when you touch it

Question 6

Why does water boil when it reaches its boiling point at a given pressure?

At boiling, vapor can form throughout the liquid rather than only at its surface.

All water molecules are destroyed Gravity stops acting on the water Its vapor pressure becomes equal to the surrounding pressure, allowing vapor bubbles to grow in the liquid The water permanently stops absorbing energy

Question 7

Why does soap make it easier to remove oily grease from your hands?

Soap molecules can interact with both water and oily substances.

Soap converts all grease into pure water Soap helps surround grease so it can be carried away by water Soap makes water completely solid Soap removes the need for water in washing

Question 8

Why are electrical wires commonly made with a metal core such as copper?

Think about the property needed to allow electric current to flow efficiently.

Copper completely blocks electric current Copper generates unlimited electricity by itself Copper has no electrons Copper is a good conductor of electricity

Question 9

Why can a drinking straw draw liquid upward when you suck on it?

Sucking changes the pressure inside the straw compared with the pressure on the drink.

Atmospheric pressure pushes the liquid upward when pressure inside the straw is reduced Gravity reverses direction inside the straw The liquid loses all of its mass inside the straw The straw becomes magnetic and attracts the liquid

Question 10

Why do wet clothes generally dry faster on a warm, breezy day?

Think about evaporation and the movement of moist air away from the clothes.

Moving air destroys the water molecules Sunlight physically squeezes water from the fabric Warmth and moving air increase the rate of evaporation Wind turns liquid water directly into ice

Question 11

Why does a thermos flask help keep a hot drink hot for longer?

Think about reducing the ways heat can move between the drink and its surroundings.

It continuously produces new heat without energy It increases the boiling point until the drink cannot cool It permanently freezes the air around the drink Its design reduces heat transfer between the contents and the surroundings

Question 12

Why does food often cool faster when spread across a wide plate instead of being kept in a deep pile?

Think about how much of the food is exposed to the surrounding air.

A larger exposed surface area allows faster heat transfer to the surroundings Gravity becomes weaker when food is spread out Spreading food prevents its molecules from moving The plate removes all thermal energy instantly

Question 13

Why does a sharp knife generally cut food more easily than a blunt knife when the same force is applied?

Consider how the applied force is distributed over the knife's edge.

A sharp edge applies greater pressure over a smaller area A sharp knife always weighs much more A sharp knife automatically heats the food A sharp knife removes gravity from the food

Question 14

Why does a pressure cooker usually cook food faster than an ordinary open pot?

Consider what increased pressure does to the boiling point of water.

Higher pressure allows water to reach a temperature above its normal boiling point Pressure completely stops heat from escaping The cooker makes food lighter in weight The cooker removes all water from the food

Question 15

Why is a small gap often left between sections of railway tracks or other long metal structures?

Think about what usually happens to metal when its temperature increases.

Metal completely disappears in hot weather The gaps allow room for thermal expansion The gaps allow trains to recharge their batteries The gaps increase the gravitational pull on the rails