Forces and energy Flashcards
How does a bulb transfer energy?
Electricity transfers energy to an electric bulb which then transfers the energy to the surroundings by light and heating
What is work done?
Energy transferred by a force
What does the amount of work done depend on?
The size of the force and how far the force has moved
What is power?
The rate at which energy is transferred
What is the relationship between watts and joules?
1 watt is one joule of work per second
What is a contact force?
the force between two touching objects
What is the normal contact force?
An object at rest on a surface exerts a force on the surface. The reaction force acts at right angles to the surface called the normal contact force
What is water resistance a form of?
friction
If a boat is moving what forces is it experiencing?
- Water resistance
- Force from the engine
- Upthrust
- Gravity
What is upthrust balanced out by?
Gravity (non-contact force)
What is gravity?
A force that occurs between any two objects that have mass
Why does the moon stay in orbit around the Earth?
Because the two bodies are attracting each other (force of the moon on the earth is the same size of the force of the earth on the moon in the opposite direction)
What are vectors (in this instance)
Arrows that show both magnitude and direction (in showing the forces of gravity between two bodies)
What is an action-reaction force?
Pairs of forces acting on different objects, in opposite directions
What is a force field?
A space around an object where it can affect other objects
What are forces that affect objects they’re not in direct contact with
Magnetism
Static Electricity
What is a magnetic field?
The space around other materials where it can affect other materials
What is an electric field?
An object that is electrostatically charged’s area around it which can affect other objects in that area (two objects close to each other in the field with the same charge produce equal and opposite directional forces)
If the resultant force is zero, what does this mean?
The forces acting on the object are balanced
What happens to the forces on an aeroplane travelling at a constant force?
The horizontal and vertical forces are equal and the resultant force is 0
What is a free body force diagram?
A diagram to model the forces acting on an object
When do we use scale diagrams?
When you need to find the resultant force in an instance that the forces acting on an object are not acting along the same line
How do you draw a scale diagram?
- Draw arrows at the correct angles to represent the forces (the length should represent the size of the force (use a scale))
- Draw lines to make a parallelogram
- The resultant force is the diagonal of the parallelogram and measure this line and use the scale to find the resultant force
What helps an aeroplane to fly steeper?
Thrust
How can you work out the amount of thrust is pushing the aeroplane upwards and forwards?
By resolving the thrust force into two component forces at right angles to each other (using a scale diagram)
How do you draw a scale diagram to help with resolving a force (e.g thrust)
1) Draw a force arrow (e.g thrust) to scale at the correct angle (e.g 30 degrees at 200kN)
2) Draw a rectangle with the sides in the direction you are interested in e.g horizontal or vertical
3) The line lengths that line up with the force line (in out example 200kN) and measure - use the scale to find size
What is a moment?
A turning force
What does the moment of a force depend on?
The size and where the force is applied - greater the force and the further away it is from the pivot (the point around which the object can rotate) the greater the moment
What is the normal?
The distance between the force and the pivot, right angle to the direction of the force
What is the unit for moment?
Newton metres (N m)
What does it mean when a system involving rotational forces are in equilibrium?
The sum of the clockwise movements = the sum of the anticlockwise movements
What is a lever?
A bar that pivots about a point and is used to transfer a force
What is effort?
Force from a man onto a lever
What is the load?
Force of object on lever
How do gears turn other gears?
The teeth of one gear fits into another and so as one moves, so does the other
If one gear as 8 times as many teeth as the second, how many turns will it take of the smaller for one rotation of the larger one
8 turns of the smaller one for one rotation of the larger
