SP2- Motion And Forces Flashcards
(52 cards)
What is the difference between a vector quantity and a scalar quantity
vector quantities has direction and magnitude
Scalar quantities only have magnitude
What’s acceleration
Is a change in a vector quantity (velocity) acceleration is also a vector
What type of quantity is a force
A vector
How is the size of the force represented in a diagram
The length of the arrows
What is the resultant force
The overall force of an object
How do yu work out the resultant of 2 forces
If the forces are acting in the same direction add them
If they are acting in opposite directions subtract them
What happens if the resultant forces of an object is 0
The forces are balanced
If there is a non zero resultant force on an object the forces are unbalanced
What’s Newton’s first law of motion
A moving object will continue to move at the same speed and direction unless an external force
Acts on it
A stationary object will remain at rest unless an external force acts on it
How could forces change the speed and/or direction of an object
If there are balanced forces it will not change
If there are unbalanced forced the speed and/ or direction of an object will change
What’s the centripetal force
The resultant force that causes the change in direction
Eg an object moving in a circle has changing velocity even though it’s speed remains the same
Tell me about the centripetal force
Acts towards the centre of a circle
Other types of force that can make objects move in circular paths include friction and gravity
What is mass
The quantity of matter there is in an object
It only changes if the object itself changes
Units are kilograms
What is weight
A measure of pull of gravity of an object and depends on the strength of gravity
Units are newtons
How can weight be measured
Using a force meter which has a scale in newtons
Many contain a spring which stretches as the force on it increases allowing her weight to be read of the scale
What’s the earths gravitational field strength
10 N/kg
Every kg is pulled down with a force of 10 newtons
The field strength is different on other planets and moons
Tell me the triangle that links weight, mass and gravitational field strength
W on the top (weight) and m(mass) X gravitational field strength on bottom
How does air resistance increase
With speed
What is newtons Second law of motion
The acceleration in the direction of a resultant force depends on
The size of the force (for same mass, bigger force bigger acceleration)
The mass of an object (for the same force, the more massive the object the smaller the acceleration)
How do you calculate force
Force (n) = mass (kg) X acceleration (m/s^2)
What’s the inertial mass
The inertial mass of an object is the force on it divided by the acceleration that force produces
The more massive an object is - the more force is need to change its velocity.
Tell me about Newton’s third law
It’s about the forces on two different objects when they interact with eachother
This interaction can happen;
When objects touch- such as when you sit on a chair
At a distance, such as the gravitational attraction between the earth and the moon
What are action-reaction forces
There is a pair of forces acting on the two interactive objects
The two forces are Always the same size and in opposite directions, they are also the same type of force
What’s a equilibrium situation
When nothing is moving eg when a there is a tug of war
How are action-reaction forces different to balanced forces
In both cases the sizes of the forces are equal and act in opposite direction but:
Action-reaction forces act on different objects
Balanced forces all act on the same object
