Forces and Motion, Electricity Flashcards
(53 cards)
What do lorries and caravans have?
Deflectors - to make them more streamlined and reduce drag.
What’s the most important factor in reducing drag in fluids?
Keep the shape of the object streamlined
What are the two types of friction and how to reduce?
Static friction (gripping surfaces) and sliding friction (sliding past each other surfaces)
Put a lubricant e.g. oil or grease between the surfaces.
What happens in a fluid if speed increases?
Friction always increases as the speed increases!
What are the different types of energy?
Thermal Kinetic Nuclear Sound Light Electrical Chemical potential Gravitational potential Elastic potential
T K N S L G C E E
Vector quantities?
Have size AND direction!
Eg force, velocity, displacement, acceleration, momentum
Scalar quantities?
only size.
Eg mass, temperature, time, length, distance
What’s air resistance?
The force that acts in the opposite direction to the motion of an object moving through the air.
(Depends on the shape and speed of the object)
What’s contact force?
The equal and opposite forces that two objects exert on each other when pushed together.
The contact force from the ground pushes up when standing still (against the weight pushing down)
What’s friction?
The force that opposes motion.
What’s gravitational force?
The force that pulls objects towards earth. (Weight) the earth pulls with a force of about 10 newtons in every kilogram of mass.
What is thinking distance and what affects it?
The distance the car travels while the driver is reacting (between the driver noticing the hazard and applying the brakes)
Affected by: speed, tiredness, drugs, alcohol, talking
What is braking distance and what affects it?
The distance the car travels from when the brakes are being applied until the vehicle stops
Affected by speed, icy roads, faulty brakes (road quality, weather conditions, tires, mass of car)
What is stopping distance?
Thinking distance + braking distance
What is Newton’s third law?
For every action there is an equal and opposite reaction.
Where does weight act from?
The weight of a body acts through its centre of gravity.
What is elastic behaviour?
The ability of a material to recover its original shape after the forces causing deformation have been removed.
What is the initial linear region of a force-extension graph associated with and what is that?
Hooke’s law!
Load is directly proportional to the extension of an object, provided you don’t surpass an object’s elastic potential
What’s electrostatic force?
Between two charged objects. (Direction depends on type of charge)
What’s tension?
In a rope or cable
What’s Newton’s first law?
When forces are balanced, an object is either stationary or moving at a constant speed.
What’s Newton’s second law?
When forces are unbalanced, an object will accelerate in that direction.
Explain safety in cars:
To reduce the size of the force acting during deceleration, must increase time taken to bring car to rest.
Eg crumple zones crumple on impact (increasing time taken for car to stop), seat belts stretch slightly (increasing time taken for wearer to stop- reduces force on chest), air bags slow person down gradually
Is gravitational field strength the same everywhere?
Gravitational field strength is how strongly something pulls an object towards it.
Earth has a higher gravitational field strenght than the moon: on earth we are pulled down so much that we can jump only for a few seconds; on the moon the time you can jump for is longer as it is pulling you back in with a weaker gravitational field. It’s also different on other planets…
The reason for this difference - earth has more mass than the moon and so has a bigger gravitational field strength. Planets with a larger mass than earth will have a higher gravitational field strength.
