P2 Part A Flashcards
What is the difference between speed and velocity?
Speed is how fast an object is travelling, and velocity is the same but with direction specified too
What does the gradient of a distance time graph tell you?
How fast the object is travelling
How do you calculate speed from a distance/time graph?
Speed = Gradient = vertical ÷ horizontal
What is acceleration?
Acceleration is how quickly the velocity is changing. This change in velocity can either be a change in speed or a change in direction.
What is the formula for acceleration?
acceleration = change in velocity(final velocity - initial velocity) ÷ time taken
What is the unit used for acceleration?
m/s2
What is the formula for calculating acceleration in a certain time fram from a V-T (Velocity-Time) graph?
Acceleration = gradient = Vertical (velocity) change ÷ Horizontal (time) change
What force is the force of attraction between all masses?
Gravity
On the …… of a planet, …… makes all things ……. towards the ground (all with the same acceleration, which is about …. m/s2 on Earth)
On the surface of a planet, gravity makes all things accelerate towards the ground (all with the same acceleration, which is about 10m/s2 on Earth)
What is ‘mass’?
Mass is the amount of substance in an object. For any given object this will have the same value anywhere in the universe (measuref in g/kg)
What is ‘weight’? How can it be measured?
The weight of an object is the amount of gravity acting on an object (measured in Newtons). This will be different on different planets due to varying gravitational forces on each.
Weight can be measured using a spring balance or newton meter.
What is the formula for working out the weight of an object?
weight = mass x gravitational field strength
What is the resultant force of an object?
A resultant force is the total force on an object, taking into account forces in both directions
eg. on a car the total of the driving force - air resistance
What happens if the resultant force on a stationary object is 0?
It will stay stationary
What happens if there is no resultant force on a moving object? How does this effect velocity?
If there is no resultant force on a moving object, it will carry on moving at a steady speed. There will be no change in velocity.
What does it mean if an object has a resultant force? How is this shown on a force diagram?
It means that the object will accelerate in the direction of that resultant force. On a force diagram, this will be shown by arrows that are unequal.
What is the equation for resultant force? How can this be rearranged to work out acceleration?
Resultant force = mass x acceleration
(F = ma)
Acceleration = resultant force ÷ mass
(a = F/m)
Fill in the gaps:
When two objects interact, the …… they exert on each other are …… and ………..
When two objects interact, the forces they exert on each other are equal and opposite.
If two objects interact with equal and opposite forces, how does anything ever move anywhere?
The different objects will have different masses, meaning they accelerate at different speeds (a = F/m)
Why does friction always slow objects down? When does friction occur?
Friction always acts in the opposite direction to movement. Friction happens between two surfaces when they come in to contact with one another, or when an object passes through a fluid (drag).
Why are cars streamlined? And why do parachutes have a large surface area?
Cars are streamlined to reduce the area available for resistive forces to work on (eg. air resistance), as they slow moving objects down (and would make the engine work harder).
A parachute, on the other hand, has a large surface area to so that the area resistive forces (drag) can work on is greater, making for a slow and gentle landing.
Drag increases with speed - true or false?
True. car has much more friction to work against when travelling at 70mph compared to 30mph. This means the engine will have to work much harder to maintain a steady speed.
Outline the three stages of a falling object
- At the start, the object accelerates downwards because of its weight. There is no air resistance. There is a resultant force acting downwards.
- As it gains speed, the object’s weight stays the same, but the air resistance on it increases. There is a resultant force acting downwards.
- Eventually, the object’s weight is balanced by the air resistance. There is no resultant force and the object reaches a steady speed, called the terminal velocity.



