P5 - Forces Flashcards
What are forces? Are they vector or scalar?
What are the examples of the 2 types of forces?
Force = a push or pull in a particular direction.
Forces are vector quantities because they have both magnitude & direction
Contact forces:
• friction, upthrust, air resistance, push/pull
Non contact forces:
• weight, electrostatic, magnetic
What are vectors and scalars?
Scalar = a quantity that has size (magnitude) but no direction
• time, distance, speed, energy, mass, temperature
Vector = a quantity that has a size (magnitude) and direction
• force, displacement, velocity, acceleration, weight, momentum
What is Newton’s first law?
An object remains at rest (or if in motion remains in motion) at a constant velocity, unless acted on by an external force.
What is Newton’s second law?
F = m a
Resultant force = mass x acceleration
What is Newton’s third law?
Whenever two objects interact, the forces they exert on each other are equal and opposite.
What is inertia?
The tendency for motion to remain unchanged.
What is gravitational force?
What are it’s 2 effects?
Gravitational force = the force of attraction between masses.
• Gravity attracts all masses but it is only noticeable when the mass is really big.
Gravitational force has 2 effects:
• makes everything fall towards ground
• gives everything a weight
What is the difference between mass and weight?
Mass = the amount of stuff in an object
• Is the same value anywhere in the universe
• Measured in Kg - using balance, scales
Weight = the force acting on an object due to gravity
• Is different in different locations
• Measured in N - using newton meter
What is the equation of weight?
Weight = mass x gravitational field strength
(N) = (kg) x (N/kg)
What is the equation for momentum?
What is the conservation of momentum?
P=mv
Momentum = mass x velocity
In a closed system, the total momentum before an event (e.g. a collision) is the same after the event.
What is resultant force?
How is it represented?
Resultant force = the overall force on an object
Free body diagram
(The size of the arrow represents the size of the force)
What is acceleration?
What is the equation for acceleration?
What is deceleration?
Acceleration = how quickly something is speeding up (m/s^2)
Acceleration (m/s^2) = change in velocity (m/s) / time (s)
Deceleration = negative acceleration (slowing down)
What equation is only used when acceleration is in uniform?
V^2 - U^2 = 2as
Final velocity - initial velocity = 2 x acceleration x distance
What is the trolley practical?
What are light gates?
To investigate the effect of mass on acceleration we place the masses on the trolley
To investigate the effect of force on acceleration we place more masses on the string
Light gates are pieces of equipment that measure speed over a distance.
Speed = distance/ time
Work done
