P4 - Explaining Motion Flashcards
Give two units of speed
m/s and km/h
Displacement
The distance an object is from its starting point
Velocity
An object’s speed in a certain direction
What is the speed equation?
Speed = distance / time
What is the Average velocity equation?
Average velocity = displacement / time
What is the displacement equation?
Displacement = Acceleration x Time
Acceleration
The rate at which the speed of an object increases
What is the Acceleration equation?
Acceleration = Change in speed / Time
What are the units of Acceleration?
Metres per second squared = m/s^2 OR m/s/s
What is another word for negative acceleration?
Deceleration
What is a repulsive force? and what force does it oppose
A force which pushes objects apart and it works against an attractive force which pulls objects together
What is the opposing force to gravity?
Reaction
What are vector quantities?
Quantities like Forces that have both magnitude (size) and direction
What is friction?
A force that acts on two surfaces as the slide over one another
The size of the friction force depends on: (2)
- the roughness of the surfaces
- how hard they are pushed together/ how heavy they are
Limiting friction
When friction reaches a certain maximum value and objects start the move
Why is Lubrication used to reduce friction in machinery?(2)
To stop the parts getting too hot and wearing out
How does friction work when you walk? (3)
Your feet push against friction so the floor pushes your foot forwards.
The resultant force is a combination of friction and the surface reaction
They combine to push the foot in a diagonal upwards direction
Resultant force
The total or overall force acting on an object
What is Newton’s first law?(3)
When resultant force = 0, the forces are balanced and acceleration is 0. The object will either:
•be still
•move continually at a constant speed
What is Newton’s third law? (3)
When forces are unbalanced, an object will either have a:
•change in speed
•change in direction
Gravity
A force which pulls all object towards the centre of the Earth
What force opposes gravity when object are falling through the air?
Air resistance/ drag
The ____ the object’s surface area, the _____ the drag force
Larger, larger :D
Terminal velocity
The constant maximum speed reached by a falling object
The size of the force exerted during a collision depends on: (3)
- the mass of the object
- the speed of the object
- the duration of the impact
What are the four car safety devices?
Air bags, crumple zones, seat belts, crash helmets
What do seat belts do to protect passengers? (2)
Stretch to increase the impact time
Hold a person in the car
What do crumple zones do to protect passengers? (2)
Increase the time to stop, the impact force
Decrease the kinetic energy
What do air bags do to protect passengers? (1)
Increase the time it takes for the momentum to reach 0
What is the equation for momentum?
Momentum = mass x velocity
What is the equation for change in momentum?
Change in momentum = resultant force x time which it acts
What are the units of force?
Newtons
What are the u it’s of momentum?
kg m/s
Work done
The energy used by the movement of a force
What are the units of work done?
Joules
Energy + units
The ability to do work, measured in joules
What is the equation for work done? With units
Work done(J) = Force(N) x Distance moved in the direction of the force (m)
As you raise an object, the Gravitational potential energy _____ and as an object falls the gravitational potential energy ______
Increases as raised and decreases as falls
What is the equation for change in GPE with units?
Change in Gravitational potential energy (J) = weight (N) x Vertical height (m)
What is the equation for kinetic energy with units?
Kinetic energy (J) = 1/2 x Mass (kg) x Velocity squared (m/s^2)
Remember this! :)
The work done by a force is the same as the change in kinetic energy
When an object falls its ________ is transferred to ________
Gravitational potential energy is transferred to Kinetic energy
What are the 5 energy changes when someone does a pole vault?
- Running
- Using the pole
- Launching above the obstacle
- Falling towards the ground
- Landing on the ground
- Kinetic energy
- Elastic energy
- GPE
- Kinetic energy
- Heat and Sound energy
When a ball is bounced, when the ball is high the ____ is high and when the ball is the low the _____ is high
High ball = High GPE
Low Ball = High KE
Speed
How far an object travels in a certain amount of time
