SP8/9 - Forces Doing Work/ Forces and their Effects Flashcards
What is the equation for work done?
Work done (J) = force (N) x distance moved in the direction of the force (m)
E = F x d
What is power?
The rate at which energy is transferred. It is measured in watts (W) (1 watt = 1 joule is transferred per second)
What is the equation for power?
Power (W) = work done (J) / time taken (s)
P = E/t
What is work done?
The energy transferred by a force.
What are the three non-contact forces?
- gravity
- magnetism
- electrostatic
What are the properties of a gravitational field?
- objects are pulled towards the centre of mass
- it can only act in one direction
What are the properties of a magnetic field?
- the force acts from North to South
- the force is strongest at the poles
- the force can act in two directions
- can attract magnetic materials (iron, steel, nickel, cobalt) and attract or repel other magnets (N+S = attract, S+S = repel, N+N = repel)
What are the properties of an electrostatic field?
- the force moves away from positive towards negative
- it can act in two directions
What is a force field?
The space around an object where it can affect other objects.
What is a free body force diagram?
A picture showing the forces that act on a body. Dots or rectangles represent the object.
How do you draw a vector diagram?
- Create a scale (e.g. 5kN = 1cm)
- draw lines at the correct angles (it will tell you what angle this is in the question)
- connect the lines to draw a parallelogram
- draw a line across the diagonal of the parallelogram
- measure it’s length and use the scale to work out the resultant force
What is the equation for moment?
Moment of a force (N m) = force (N) x distance perpendicular to the direction of the force (m)
What is true of the moments in a system that is in equilibrium?
Sum of clockwise moments = sum of anti-clockwise moments
