Forces and motion Flashcards
Describe an experiment to investigate the motion of everyday objects
- Measure out a height of 1.0 m using the tape measure or metre ruler
- Drop the object (paper cone or tennis ball) from this height, which is the distance travelled by the object
- Use the stop clock to measure how long the object takes to travel this distance
- Record the distance travelled and time taken
- Repeat steps 2-3 three times, calculating an average time taken for the object to fall a certain distance
- Repeat steps 1-4 for heights of 1.2 m, 1.4 m, 1.6 m, and 1.8 m
What errors should you keep in mind for the tennis ball/dt experiment?
- measurements on the tape measure or metre rule are taken at eye level to avoid parallax error
- using an electronic sensor, such as light gates, to obtain highly accurate measurements of time
- done in a space with no draught or breeze, as this could affect the motion of the falling object
- ball bearing and an electronic data logger, like a trap door, is a good way to remove the error due to human reaction time for this experiment
define acceleration
rate of change of velocit
what does a velocity time graph show
how the velocity of a moving object varies with time
what other info does v time graph show
If the object is moving with a constant acceleration/deceleration
The magnitude of the acceleration/deceleration
what does area under a VT line represent
displacement
what are scalars
quantities that have only a magnitude
what are vectors
both a magnitude and a direction
what’s friction
The force which opposes the motion of an object
what’s weight
The force acting on an object due to gravitational attraction
what does weight do?
- Objects stay firmly on the ground
2.Objects will always fall to the ground
- Satellites are kept in orbit
define ‘stopping distance’
The total distance travelled during the time it takes for a car to stop in response to some emergency
whats the eq for stopping distance
Stopping distance = Thinking distance + Braking distance
what factors affect stopping distance?
VEHICLE SPEED - the greater the speed, the greater the vehicle’s braking distance will be (because the brakes will need to do more work to bring the vehicle to a stop)
VEHICLE MASS - a heavy vehicle, such as a lorry, takes longer to stop
ROAD CONDITIONS - wet or icy roads make it harder to decelerate
DRIVER REACTION TIME - a driver’s thinking distance depends on their reaction time. Being tired, or intoxicated (i.e. alcohol, or drugs) can increase reaction time
What 2 forces do falling objects experience?
Weight (due to gravity)
Air resistance (due to friction)
describe terminal velocity
- UPWARDS AIR RESISTANCE is very small because the skydiver isn’t falling very quickly
- there are UNBALANCED FORCES on the skydiver initially
- As skydiver speeds up, air resistance increases, eventually growing large enough to BALANCE the downwards weight force
- Once air resistance equals weight, the forces are BALANCED
- no longer any RESULTANT force
- skydiver’s acceleration is zero - they now travel at a CONSTANT SPEED
- This speed is called their TERMINAL VELOCITY
Core Practical 2: Investigating Force & Extension
(can be used for both spring and rubber band)
- Set up APPARATUS
- Align the marker to a value on the ruler, record this INITIAL LENGTH of the spring
- Add the 100 g MASS hanger onto the spring
- RECORD the mass (in kg) and position (in cm) from the ruler now that the spring has extended
- Add another 100 g to the mass hanger
- RECORD the new mass and position from the ruler now that the spring has extended further
- REPEAT this process until all masses have been added
- REMOVE the masses and REPEAT the entire process again, until it has been carried out a total of three times, and an average length is calculated
Investigating force-extension apparatus for a metal (e.g. copper) wire
- Set up the apparatus so the WIRE IS TAUT
- Measure the ORIGINAL LENGTH of the wire using a metre ruler and mark a REFERENCE POINT with tape near the beginning of the scale
- Record the INITIAL reading on the ruler of the reference point
- Add a 100 g MASS onto the mass hanger
- Read and record the NEW READING of the tape marker from the meter ruler now that the metal wire has extended
- REPEAT this process until all masses have been added
- Remove the masses and repeat the entire process again, until it has been carried out a total of three times, and an average length (for each mass attached) is calculated
WHAT DOES HOOKE’S LAW STATE
The extension of an elastic object is directly proportional to the force applied, up to the limit of proportionality
when does elastic deformation occur
When objects return to their original shape when the stretching force is removed
when does inelastic deformation occur
When objects remain stretched and do not return completely to their original shape even when the stretching force is removed
