Newtons laws Flashcards
What is inertia?
Inertia is the opposition of an object to a change in its motion. Bigger the object, larger the inertia.
What is Newtons first law?
‘An object at rest stays at rest, or an object in motion stays in motion with the same speed and the same direction, unless acted upon by an unbalanced force.’
What is Newtons second law?
It is summarised by the equation - resultant force = mass × acceleration.
The acceleration of an object increases if the resultant force on it increases, and decreases if the mass of the object increases.
What is the difference between a resultant force and a balanced forces?
A resultant force acting on an object causes a change in its motion. Balanced forces cause an object to remain stationary or move at a constant speed.
What is mass (m) measured in?
Kilograms, kg.
What is meant by the weight of an object?
The weight of an object is the force of gravity acting on the objects mass.
What is weight measured in?
Newtons, N.
On Earth, what is the weight of a 1kg object?
10 newtons. The weight of any object on Earth can be calculated by multiplying its mass (kg) by 10.
What is the equation to find weight?
weight (N) = mass (kg) x gravitational field strength (N/kg)
Explain the process of jumping out of a plane in terms of weight.
As they jump, the weight will remain constant. Initially, the only resultant force on the jumper is their weight, so they begin to accelerate downwards. As they will speed up, the force of air acting upwards on her increases. Eventually, it is equal and opposite to their weight - the two forces are equal in size but acting in opposite directions, so they are balanced. They will fall at a constant or terminal speed from then on wards.
What is Newtons third law?
‘In an interaction between 2 objects, a and b, the force exerted by body a on body b is equal and oppositely directed to the force directed by body b on body a.’
‘For every action force, there is an equal and opposite reaction force.’
What forms an interaction pair?
The force on one object is called an action force, the force on the other object is called the reaction force. Together they form an interaction pair. The action force and the reaction force are equal and opposite. But they do not cancel each other our because they act on different objects.
What are the 3 things you need to remember when considering interaction pairs?
1 - the two forces in the pair act on different objects.
2 - the two forces are equal in size but act in opposite directions.
3 - the two forces are always the same type, for example contact forces or gravitational forces.
What are 2 types of forces?
Contact forces - where objects need to come into contact with each other to exert the force.
‘action at a distance’ forces - such as gravity or electromagnetic forces, where it is not physically touching.
