P5- Forces Flashcards
What are scalar quantities
Quantities which have magnitude only
What are vector quantities
Quantities which have magnitude and direction
What are examples of scalar quantities
Mass, temperature, speed, energy
What are examples of vector quantities
Displacement, weight, force, velocity, acceleration
What can be used to show the direction of the vector
An arrow head
What type of quantity is a force
Vector quantity
What is force measured in
Newtons
What’s the two types of forces
Contact and noncontact
What is a contact force
When two objects are physically touching
What are examples of a contact force
Tension, Friction, air assistance and normal contact force
What is a noncontact force
Two objects are physically separate
What are examples of noncontact forces
Gravitational force, electrostatic force and magnetic force
What quantity is mass and why
Mass is scaler as it has no direction
Why is weight a vector quantity
Because the gravitational field strength causes a force downwards on the object
What is gravitational field strength
A measure of the force of gravity in a particular location 
How do you calculate weight
Mass x Gravitational field strength
What is the centre of mass
The single point where the weight acts on an object
What’s a resultant force
A single force has the same effect as all the original forces acting together
How is resultant force measured
Taking away the smaller force from the larger force
How do you calculate work done
Force x distance
What is elastic deformation
When elastic materials return to original size after force has acted on it
What is inelastic deformation
When inelastic materials don’t return to original shape when the forces are removed
What equation links force spring constant and extension
Force = spring constant x extension
What is a moment
The turning effect of a force
How do you calculate moment
Force x distance
What is a balance moment
When the clockwise moment equals anticlockwise moment
What is a lever
It allows large weight to be lifted with relatively small amount of force
What are fluids
Gas and liquids
What is the atmosphere
A thin layer of air around the Earth
What happens to the atmosphere when you increase the altitude
It gets less dense
What happens to atmospheric pressure with an increase in height
The pressure decreases
What is upthrust
The resultant force caused by the greater pressure on the bottom of the surface then on top of the surface
What is distance
How far an object has moved
What is displacement
The distance an object moves in a straight line and in what direction
What is a normal walking speed
- 5 m/s
What is a normal running speed
3 m/s
What is a typical cycling speed
6 m/s
What factors does speed depend on
Age fitness terrain and distance
What is velocity
Speed and direction
Does the velocity change when an object moves at a constant speed in a circle
Yes because the direction changes
What does a distance time graph show
The distance travelled along a straight line
What is acceleration
The change in velocity over a period of time
What does the gradient of a velocity time graph show
Acceleration
When an object falls towards the surface of the Earth what is the acceleration of the object
9.8 m/s
What is terminal velocity
When an object stops accelerating and moves at a constant velocity
What is Newton’s first law of motion
If the resultant force acting on a stationary object is zero the object will remain stationary.
Furthermore if the resultant force of a moving object is zero object to move at the same direction and speed.
What is newton second law of motion
The acceleration of an object is proportional to the resultant force acting on the object and inversely proportional to the mass of the object
What is inertia
The measure of how difficult it is to change the velocity of an object
What is Newton’s third law of motion
Whenever two objects interact, The forces they exert on each other are equal and opposite
- What happens when a skydiver jumps out of the plane
The velocity increases as weight is the only force acting on the skydiver
Does the weight change during the skydive
No the weight Is always the same
- What happens to the skydiver as it falls
The skydiver experiences friction with air molecules the force of friction acts upwards
2. As the skydiver falls, why does the diver continue to accelerate
The weight is greater than the air assistance
- What is the effect of the velocity increasing
The air assistance increases
- When does the skydiver reach terminal velocity
When the forces balance causing no resultant force and the velocity to be constant
- When does the surface area of the skydive increase
When the parachute opens
- What is the effect of the parachute opening and increasing the surface area
The air resistance increases meaning the result of forces acting upwards so the skydiver decelerates
- When does the skydiver hit the ground
When the weight balances air resistance again but this time at a lower terminal velocity
What is the stopping distance
The total distance travelled from when the driver spots the obstruction to when the car stops
What is the thinking distance
The distance travelled by the car during the drivers reaction time
What is the reaction time
The time taken to spot the obstruction, make a decision and move the foot to the brake
What is the breaking distance
The distance the car travels from when the driver applies the brakes to when the car stops
What’s a typical reaction time
0.2 to 0.9 seconds
What factors increase reaction time
Alcohol drugs tiredness distractions 
What factors increase breaking distance
Wet or icy conditions, Worn tires
What factors increase breaking distance
Wet or icy conditions, Worn tires
What happens during breaking in a car
Friction increases between the brake and the wheel, this causes kinetic energy to convert to thermal energy meaning the temperature increases at the brake
How much momentum does a stationary object have
Zero
What is the conservation of momentum
In a close system the total momentum before an event is equal to the total momentum after an event
Describe what happens during a car crash in terms of momentum
The momentum of the passengers decreases rapidly from large Amount to 0 in less than a second. This places huge forces on passengers
How can the danger of huge forces of momentum be decreased
By increasing the time of impact
What components within a car help to slow down momentum change
Airbags and seatbelts 
