Force and Motion Flashcards
What is a force?
A push or a pull.
What is a resultant force?
The overall force acting on an object.
How do you calculate resultant force?
- Adding up all forces in the same direction.
- Subtracting all forces in opposite directions.
- e.g. 30N to right and 10N to left = 20N to the right.
How can you summaries Newton’s First Law?
An object remains at rest or travels at a constant speed in the same direction unless acted on by an unbalanced force.
What is an inertia?
The tendency of an object to remain stationary, or resist changing velocity. e.g. the Earth has a huge inertia.
What is a terminal velocity?
The motion of a falling object when weight and air resistance are equal.
What is a free body force diagram?
A diagram where you show all the forces acting on an object.
What is a vector diagram for?
It calculates the resultant force of two forces acting at a right angle of each other.
What mathematical equation do you have to use for a vector diagram?
Pythagoras Theorum.
How can you summarise Newton’s Second Law?
- An unbalanced force acting on an object will cause it to accelerate.
- The acceleration will be in the same direction as the unbalanced force.
- The acceleration is proportional to the unbalanced force.
- The acceleration is inversely proportional to the mass.
What is an inertial mass?
How hard it is to change the velocity (speed or direction) of an object.
How can you summarise Newton’s Third Law?
- Every action has an equal and opposite reaction.
- Forces act in pairs. These forces are:
Equal in magnitude.
Opposite in direction.
The same type of force.
Acting on different objects.
What does mass do?
It tells us how much matter is in an object.
What is mass measured in?
Kilograms (kg).
What is weight?
The force acting on an object due to gravity.
What is weight measured in? (remember: weight is a force)
Newtons (N).
What does the weight of an object depend on?
Gravitational field strength.
What can you measure the weight of an object with?
A newtonmeter.
What is the centre of mass of an object?
The weight of an object mat be considered to act at a certain point called the ‘centre of mass’.
What is required for an object to be stretched, compressed or bended?
More than one force needs to be applied.
What is a deformation?
Any change in shape of an object.
What is elastic deformation?
Where an object returns to it’s original shape.
What is inelastic deformation?
Where an object doesn’t return to it’s original shape.
What is extension?
The amount an object stretches.
What does Hooke’s Law say?
- The extension of an object is directly proportional to it’s stretching force.
- The equation is Force = spring constant x extension.
What happens when an object is stretched beyond the limit of proportionality?
It will be deformed inelastically and won’t obey Hooke’s Law.
What does momentum do?
- It tells us how hard it is to stop an object.
- It gets larger with increasing mass and velocity.
Why is momentum always conserved?
The momentum before an event is the same as the momentum after the event.
What is reaction time?
The time between sensing something and moving.
What is thinking distance?
The distance a car travels between the driver knowing they have to stop and pressing the brakes.
What four factors can increase thinking distance?
- Distractions.
- Alcohol.
- Drugs.
- Tiredness.
What is braking distance?
The distance a car travels after the brakes have been applied, but before it stops.
What five factors can increase braking distance?
- Higher mass.
- Faster speed.
- Worn brakes.
- Slippery road.
- Worn tires.
What is the equation for stopping distance?
Stopping distance = thinking distance + braking distance.
