forces Flashcards
Non-Contact Forces
A force which acts at a distance, without any contact between bodies, due to the action of a field
what is the centre of mass?
the point through which the weight of an object act
state Newtons
first law:
second law:
third law:
first: if resultant force 0, obj at rest if stationary, else moves at constant speed
sec: accel of obj is proportional to resultant force of obj, and inversely proportional to mass of obj. f=ma
third: when two obj interact, they exert equal and opposite forces on each other
required practical measuring extension
-hang spring from a clamp and stand
-clamp a meter ruler alongside spring
-attach a mass hanger to the bottom of spring (100g)
-measure bottom of mass hanger when spring unstretched
-then measure hanger position when stretched
-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
-The masses are then removed and the entire process repeated again x 3 for average
what is hooke’s law
The extension of an elastic object is directly proportional to the force applied, up to the limit of proportionality
what is inertia
the tendency of an object to
continue in its state of rest or
motion
typical weight of a car
1000 kg
typical speed of a car
25m/s
state law of conservation of momentum
total momentum before a collision is equal to total mom. after collision (in a closed system)
what is a bearing
an angle measured clockwise from the north direction
what happens when changing an objects momentum in order to avoid crash
-compressible material used
-in order to increase time taken for momentum to be lost
-and lower force
how do protective pads help in collision
-(protective pads) increase the time taken to stop (during the collision)
-so the rate of change of momentum decreases
-reducing the force
what is a moment
-a rotational or turning effect of a force
levers transmit…
…the turning effect of a force
gears transmit…
….turning effects
typical braking distances for :
30 mph
60mph
70mph
-14m
-55m
-75m
typical reaction times:
0.2 s - 0.9 s
Plan an investigation to determine how the height of the ramp affects the acceleration
of the trolley.
[6 marks]
- place one wooden block under the ramp
- vary the height by placing a different number of wooden blocks
- measure the height of the ramp using a metre rule
- measure the distance travelled using a metre rule
- measure time taken using light gates (and computer/datalogger)
- measure time taken using a stopclock or ticker timer
- release trolley from the same position each time
- release the trolley without applying a force
results
* repeat at the same height and calculate a mean
* repeat for different heights
* calculate acceleration using a = (v-u)/t or a = v2- u2/2s
A vehicle drives twice as fast.
What happens to the breaking distance?
If the vehicle speed increases by a factor of 2, then the breaking distance will increase by a factor 2 squared (2²), so 4 fold.
what is terminal velocity
when an object falls in a constant velocity
what is Newton’s second law
the size of the resultant force is directly proportional to the acceleration it causes
what is inertia
the tendency for the motion of an object to remain unchanged
upthrust is caused by
pressure on the bottom of the object being greater than on top of the object
anything that gets dropped accelerates at:
9.8 m/s
