Random Flashcards
How can you change acceleration
Change in mass
Change in force
(F= ma)
What is a straight horizontal line on a distance-time graph
The car is has stopped and isn’t moving
What is a straight diagonal line on a distance-time graph
The car is moving at a constant speed.
How can you calculate speed from a distance-time graph
The gradient
What does the line in a velocity- time graph show
The gradient is the acceleration
What is the area under a velocity- time graph
Distance
At what frequency can the ionosphere reflect waves
Short frequency waves are reflected. They have to be less than 30MHz.
What waves do walls absorb
Visible light
Ultraviolet
What waves do walls transmit.
Radio waves
Microwaves
What is conduction
This is the transfer of heat through solids though passing energy and increasing the temperature of the particles in the solids next to them.
Convection
This is the transfer of energy in gases.
It is when kinetic energy of hot particles is transferred to other, colder molecules.
Example-
Hot air is less dense than colder air, because it has higher kinetic energy, meaning it can move around more. This forces the colder air to sink as it is denser and then to become heated by the heat. Then, it become hotter as it gains kinetic energy and then rise as it becomes less dense.
How do seatbelts work
It increases the time taken for the passenger’s momentum to reach 0, therefore reducing the forces acting upon it.
How do air bags work
It increases the time taken for the head’s momentum to reach 0, reducing the forces on it. It also serves as a soft cushion, preventing cuts.
How do crumple zones work
They are designed to be crushed in an accident. It absorbs energy when it changes shape, increasing the time taken for the momentum of the driver and passenger in a crash to reach 0, reducing the forces upon the car.
What is resonance
If you apply a vibration to an object at their natural frequency, they will vibrate with very big amplitudes
