Studied by 0 people
Looks like no one added any tags here yet for you.
Vector
A quantity that has magnitude and direction.
Scalar
A quantity that only has magnitude.
How to show size and direction of a force on a diagram?
With an arrow - length represents size, direction represents direction.
How to calculate resultant forces?
Add together all forces in one plane and treat the two planes separately.
Total force acting on an object
Resultant force.
Name for resultant force greater than zero
Unbalanced.
Name for resultant force equalling zero
Balanced.
What happens to the velocity of an object when the resultant force equals zero?
Stays the same.
What happens to an object if the forces acting on it are unbalanced?
Accelerates or decelerates.
Newton’s first law
An object will move at a constant speed and direction unless there is a resultant force acting upon it.
What direction does centripetal force pull?
Towards the centre of the circle.
What causes the centripetal on the moon orbiting the earth?
The force of gravity due to the earth’s gravitational field.
Mass
The amount of matter in an object.
Weight
Force applied to an object by a gravitational field.
Earth gravitational field strength
9.81N/kg can round to 10N/kg.
Two factors affecting weight
Mass and gravitational field strength.
Weight equation
Weight = mass x gravitational field strength
Unit of force
Newtons (N)
Word for change of velocity
Acceleration or deceleration.
Factors affecting acceleration
Mass and resultant force applied.
Equation form of Newton’s second law
Force = mass x acceleration
Inertial mass
The force applied to an object divided by the acceleration that force produces.
Newton’s third law
For every action force there is an equal and opposite reaction force
Equilibrium situation
When nothing is moving, therefore all the forces on an object are balanced.
Action and reaction pair of a person leaning on a wall.
Force of person on wall, force of wall pushing back on person.
Factors affecting momentum
Mass and velocity
Momentum equation
Momentum = mass x velocity
Conservation of momentum
Momentum before a collision = momentum after a collision.
How to calculate the force needed to change momentum?
Force = change in momentum / time
How to calculate stopping distance?
Stopping distance = thinking distance + braking distance
Factors affecting thinking distance
Being tired, taking drugs, drinking alcohol, using a mobile phone, speed of vehicle.
Factors affecting braking distance
Worn brakes, icy road, wet road, mass of vehicle, speed of vehicle, potholes etc. in road.
Typical human reaction time
0.25s
What is the equation we use to calculate the force acting when there is a collision?
Force = mass ( change in velocity ) / time
What does a large deceleration mean?
A very fast negative change in velocity, eg in a crash.
Dangers of a large deceleration
Injure or kill people and can damage vehicles.
Why does a large deceleration cause danger?
It means a large force will act on the people and vehicle.
How to decrease force in a collision?
Increase the time it takes to stop, eg. With crumple zones and seatbelts.
Typical road collision force
100,000N to 1,000,000N
How to tell if you are looking at balanced forces versus action-reaction pairs?
Balanced forces have all the forces acting on one object.
Action-reaction pairs are acting on two different objects.
Why is an object changing velocity when moving in a circle?
Velocity is a vector with direction and in a circle the direction is constantly changing.
What are the two forces that act on an object moving in a circle?
Centripetal and centrifugal force.
