P2.1 Flashcards
What is the unit of force?
Newtons
What can a force do to an object?
It can change the shape of an object, change its motion or change its state of rest
How are different sized forces represented on a diagram?
Arrows
What is a resultant force?
A single force that has the same effect as all the forces acting on an object
How is the resultant force calculated when two forces act on an object in the same direction?
The sum of those forces
How is the resultant force calculated when two forces act on an object in different directions?
The difference between the forces
What happens to an object when a resultant force is greater than zero?
The velocity of the object will change
What happens to an object when a resultant force is zero?
The velocity of the object will be constant or the object will stay at rest
What is the relationship between force and acceleration?
The bigger the resultant force, the greater its acceleration
What is the relationship between mass and acceleration?
The greater the mass of an object, the smaller its acceleration is for a given force
What equation relates force, mass and acceleration?
Resultant force = mass X acceleration
(N) = (Kg) X (M/S)squared
What is the unit for mass?
Kg
What is the unit for acceleration?
Metres per second squared
M/s^2
What is the difference between mass and weight?
Mass is a measure of how much stuff is in an object. Weight is a force acting on that stuff.
What is the thinking distance?
The distance travelled from when the driver sees that they need to stop to when they apply the brakes
What is the braking distance?
The distance travelled from when the driver applies the brakes to where the vehicle stops
What is stopping distance?
Thinking distance + braking distance
What is gravitational field strength?
The field of force surrounding a body in which another body would experience an attractive force.
What is meant by terminal velocity?
The maximum speed of an object, reached when the forces moving the object are balanced by its frictional forces
What is meant by work done?
How much energy is transferred
When the resultant force is zero, the forces are…?
Balanced
How is the movement of an object affected if the resultant force is zero?
~ If the object is not moving it stays where it is
~ If the object is moving it keeps moving at the same speed in the same direction
How is the movement of an object affected if the resultant force is not zero?
~ If stationary the object will accelerate in the direction of the resultant force
~ If moving the object will accelerate in the direction of the resultant force
What will the acceleration of an object depend on if an unbalanced force acts on an object?
~ The size of the unbalanced force
~ The mass of the object
The bigger the force on an object…
The greater the acceleration
The bigger the mass of an object…
The smaller the acceleration
What do you need to work out the speed of a moving object?
~ The distance the object travels
~ The time it takes to travel that distance
What can speed be measured in?
m/s or km/h
What is the difference between velocity and speed?
~ Velocity is how fast an object is moving in a given direction
~ Speed is how fast an object is moving
What is the acceleration of an object?
The rate at which its velocity changes (how quickly an object speeds up or slows down)
What two forces act on falling objects?
~ the downward force of weight, which always stays the same
~ the upward force of air resistance
The extension of an elastic object is directional proportional to what?
The force applied
What happens to an elastic object once its extension exceeds a certain value?
The force and extension stop being directly proportional
What does stretching or compressing an elastic object make it store?
Elastic potential energy
What is gravitational field strength? (10N/kg)
The force that acts on a 1kg mass at a point in a gravitational field
What is acceleration measured in?
m/s^2
When a vehicle travels at a steady speed what balances the driving force?
The resistive forces
What can affect a drivers reaction time?
~ Tiredness
~ Drugs
~ Alcohol
The faster an object moves through a fluid the greater what?
The frictional force that acts on it
What will cause an object falling through a fluid to initially accelerate?
Force of gravity
What happens when a spring is stretched?
The person stretches it and they transfer energy to the spring which it stores elastic potential energy
What is the extension of an elastic object directly proportional to?
The force applied
What is the spring constant measured in?
N/m
What do falling objects fall through?
Fluid
What is terminal velocity?
When an object is falling and the air resistance and weight become balanced and the person then falls at a steady speed
What is power measured in?
Watts
When does a spring lose its elastic potential energy?
When it is released from being stretched / squashed
What is gravitational potential energy?
The energy something has because of its position above the ground (something higher up will have a stronger GPE)
What does the weight of an object depend on?
Its mass and the amount of force it’s being pulled to the centre of earth with
How do seat belts, air bags and crumple zones increase the safety of cars?
They make the impact time longer which reduces the impact force so less damage will be done to passengers
What is Hooke’s law?
The extension of an elastic object is directly proportional to the force applied, provided the limit of proportionality is not exceeded
