P8 Flashcards
What is a Vector
A vector quantity has magnitude and direction
What is a scalar
A scalar quantity only has magnitude
3 examples of scalar quantities
Mass distance speed
3 examples of vector quantities
Displacement momentum force
What is force
Push or pull on an object that it caused by it interacting with something
2 types of forces
Contact non-contact
What is a contact force
When 2 objects have to be touching for the force to act
3 examples of contact force
Friction, air resistance, tension in ropes
What is non contact force
Object that do not need to be touching in order for the forces to act
3 examples of non contact forces
Magnetic force, gravitational force, electrostatic force
What is a resultant force
Overall force on a point or object
What happens if a resultant force moves an object
Work is done
When resultant force isn’t 0
Energy is transfered and work is done on the object
Equation for work done
Force x distance (Fs)
How does an object bend, compress or stretch
The object needs more than 1 force acting on the object
How is an object elastically deformed
If it can go back to it’s original shape
How can an object be inelastically deformed
If it can’t return to it’s original shale
When is work done in force of an object
When a force stretches or compresses an object causing energy to be transfered to the elastic potential energy store of the object
Equation linking spring constant, force, extension
Force = spring constant (N/m) x extension(m)
What is weight
The force acting on an object due to gravity
What is the gravitational field strength on earth (GCSE)
10N
How to calculate weight
Mass (kg) x gravitational field strength
What unit is weight in
Kg
A man on a bike traveled 4N north and 3N east. Calculate final magnitude direction of resultant force
5N at 37°
What does it mean to be equalibrium
The forces acting on an object add to get 0
Magnitude
Size of a quantity
Newtons third law of motion:
States that when 2 objects interact, they exert equal and opposite forces on each other
Example of newtons third law:
A boxer who punches a bag with a force of 100N experiences an equal and opposite force of 100N from the bag
Driving force:
The force that makes a vehicle move
What happens when a car moves forward?
-The force of the friction of the road on the tyre is in the forward direction
-the force of the friction of the tyre on the road is in the reverse direction
Equal and opposite forces (example):
Two roller skaters pull on opposite ends of a rope. The skaters move towards eachother because they pull each other with equal and opposite forces
Why does a tractor pull a car out of the mud
- a rope is attached to the car from the back of tractor
- the force of the mud on the tractor is greater than the force of the mud on the car
- these forces are not equal and opposite to each other
Newtons first law of motion:
If the forces acting on an object are balanced, the resultant force is zero
Example of newtons first law:
When a heavy crate is pushed across a rough floor at a constant speed without changing its direction, the push force on it is equal in size and acting oppositely to the friction on the crate
Example of an unbalanced force:
When a jet plane is taking off, the thrust force of its engine is greater than the firce of air resistance on it
What are Force diagrams?
A diagram that shows the forces acting on an object without any other objects or other forces shown
The centre of mass of a symetrical object?
For a flat object that is symmetrical, the centre of mass is along the axis of symmetry
Where is the centre of mass on an object?
The point where the mass is most concentrated
What happebs when an object is freely suspended?
It comes to rest with its centre of mass directly underneath the point of suspension
The paralellogram of forces:
-A scale diagram of two force vectors
-is uses to find the resultant of two forces not on the same line
How are the sun and earth attracted to eachother
Gravitational force
Example of a contact force in action:
A chair exerts a force against the ground, while the ground pushes back at the chair with equal force
What does the weight of an object depend on?
The strength of the gravitational fields at the location of the object
(This means the weight of an object deoends on its location)
What is force acting from?
A single point on the object, called its centre of mass
What is used to measure weight?
A calibrated spring balance
What do free body diagrams show?
All the forces acting on an object
What is resultant force?
Overall force acting on a point or object
What happens if a resultant force moves an object?
Energy is tranferred and work is done
Example of work done:
When you push something along a rough surface, you are doing work against frictional forces
When is an object in equilibrium?
If the forces on it are balanced
