Mechanics Flashcards
Define distance
The physical distance between two points
Define displacement
The distance travelled in a certain direction
Define speed
The rate of change of distance with time
Define velocity
The rate of change of displacement with time and must include direction
State the formula, with the correct SI units, for speed and velocity
v = s/t
State the formula for average speed
Average speed = Total distance/Total time
Define acceleration
The increase in velocity of a body
State the formula, with the correct SI units, used to calculate acceleration
a = v/t
State what is calculated when the area under a velocity/time graph is calculated
Distance
Distinguish between mass and weight
Mass refers to the amount of matter in an object, while weight refers to the amount of gravitional pull that the earth exerts on an object
State the formula for weight, using the correct SI units
w = m x g
Define inertia
The property of matter to resist change unless acted upon by an external force
State why it is important to wear seatbelts when travelling, referring to inertia
Seatbelts act against inertia, protecting a person from colliding with someting incase of a sudden change in speed, for example in the case of a car accident
Define a force
A push or a pull exerted on an object
Name four effects that a force can have on an object
- Change in size or shape
- An object can break
- The motion of an object can be changed
- The position of an object can be changed
Define friction
The force that opposes relative motion
Name the three factors on which the amount of friction between to objects depends
- The type of surface the object is moving on
- The amount of surface area of the object exposed to the surface
- The weight of the object
State four ways in which friciton can be reduced
- A decrease in mass
- Use rollers
- Use smooth, hard surfaces
- Use lubricants
Define work
When a force causes an object to move in the direction of the applied force, work is done on the object
Give the formula used to calculate the work done on an object
W = F x s
True or false: Simple machines reduce the amount of work needed to be done on an object. If false, elaborate on you answer
False.
The work needed to be done on the object stays the same, but simple machines reduce the force required becomes less. They therefore make the work easier
Define a lever
Simple rod pivoting around a falcrum. The object on which work is needed to be done is called the load and the force applied onto the lever is called the effort
State why pulleys move when the rope around them is pulled
Friction between the pulley and the rope causes the pulley to move with the rope
State the law of conversion of energy
Energy cannot be created or destroyed, it can only be changed from one form into another and transfered from one object onto another
State the formula for calculating the efficiency of a simple machine
Work done on load/work done by effort
Name 7 renewable resources of energy
- Solar power
- Wind power
- Hydro-electric power
- Tidal energy
- Biomass
- Geothermal power
- Wave power
State 3 advantages and 3 disadvantages of solar energy
Advantages:
- Renewable
- No pollutants or waste products
- Converts solar energy directly to electrical energy
Disadvantages:
- Low efficiency
- High initial cost
- Limited use in areas with limited sunshine
Outline two uses of a solar furnace
- Metal ore extraction
- Solar cooker
State 3 advantages and 3 disadvantages of wind energy
Advantages:
- Renewable
- No pollutants or waste products
- Low-level technology required
Disadvantages:
- Scenic pollution
- Windy site is essential
- Unreliable due to varying in wind
State 3 advantages and 3 disadvantages of hydro-electric energy
Advantages:
- Renewable
- No pollutants or waste products
- Dam water can be used for irrigation
Disadvantages:
- Limited number of usable sites
- High initial cost
- Initial disturbance of ecology
State 2 advantages and 3 disadvantages of wave energy
Advantages:
- Renewable
- No pollutants or waste products
Disadvantages:
- Insufficient capture of energy
- Visual pollution
- High maintenance
State 2 advantages and 1 disadvantages of biomass
Advantages:
- Renewable
- Low level of technology required
Disadvantages:
- Not suitable for the generation of electricity
State 1 advantages and 3 disadvantages of geothermal power
Advantages:
- Renewable
Disadvantages:
- Limited number of suitable sites
- High cost of drilling
- Danger of radioactive gases
State 1 advantages and 3 disadvantages of tidal power
Advantages:
- Renewable
Disadvantages:
- Limited number of suitable sites
- High cost in building
- Initial disturbance of ecology
State the formula used to calculate kinetic energy
Ek = 1/2mv(sqaured)
State the formula used to calculate potential energy
Ep = mgh
