P10- Force and motion Flashcards
How to investigate the effect of acceleration on an object of constant mass?
-Set up a level track with a trolley attached to string off edge of table
-Attach full weight stack to end of the string (force)
-Switch on datalogger, enter card length and release glider
-Record acceleration, do 3 times, calculate mean
-Repeat experiment with dif masses on end of string, placing mass on car instead
-Mass of car and hanger is constant
Newton’s second law of motion
Acceleration of an object is…
-Proportional to the resultant force acting on the object
-Inversely proportional to mass of the object
Inertia
The tendency of an object to stay at rest or in uniform motion
Inertial mass
Ratio of force over acceleration
How difficult it is to change the velocity of an object
When does the velocity of an object increase?
When does the velocity of an object decrease?
If resultant force is in the same direction of velocity
If resultant force is in opposite direction of velocity
Resultant force if an object falls with no other forces acting on it?
Weight
Weight
Force acting on an object due to gravity
Mass
Quantity of matter in an object
Terminal velocity
The velocity an object will eventually reach when falling, resultant force is zero.
Gravitational field strength and unit
Gravitational force on a 1kg object N/kg
Resultant force if an object falls in a fluid?
-Fluid drags on the object due to friction
-Resultant force is its weight minus the drag force
Acceleration if an object falls in a fluid
Decreases as it falls, frictional force increases
Velocity if an object falls in a fluid
-Reaches constant velocity when frictional force= weight
-Resultant force is 0
-Called terminal velocity
2 things braking force depends on
Speed of vehicle-Increases KE of car
Mass of vehicle-Increases KE of car
Stopping distance is what?
Thinking distance and braking distance
Thinking distance
Distance travelled by a vehicle in the time it takes for a driver to react
Braking distance
Distance travelled by a vehicle during the time the braking force acts
Factors that affect thinking distance and what effect they have?
Tiredness, alcohol, drugs, distractions
Increase thinking distance
Factors that affect braking distance and what effect they have?
Speed of car, adverse road conditions, condition of brakes and tyres
Increases braking distance
Law of conservation of momentum
In a closed system, the total momentum before an event is equal to the total momentum after an event
Conservation of momentum equation when two objects travel apart
(mass of A x velocity of A) = -(mass of B x velocity of B)
Conservation of momentum when two objects travel apart explained
Minus sign shows momentum of B is in opp direction to A
Both have equal and opp amounts of momentum
Total momentum after=total momentum before
Impact time affecting impact force?
The greater the impact time, the more the impact force is reduced
Force equation using time, mass, velocity
Force= mass x change in velocity / time
When two vehicles collide what 2 things are the same?
The force exerted on each other
Their total momentum
Cycle helmets and cushioned surfaces affecting impact?
Reduce impact forces by increasing impact time
Seat belts and air bags affecting impact?
Reduce impact forces by increasing impact time and spreading force across the chest
Crumple zones affecting impact?
Give way on impact so increases impact time, reduces impact force
Elastic meaning
When an object returns to original shape when forces are removed
Hooke’s Law practical
Attach spring and ruler to clamp stand
Use G-clamp to secure clamp stand
Measure original length of spring with ruler
Add one mass to spring, record its length, measure from same point
Calculate extension (new length-original)
Repeat until all masses added to spring
Plot graph
Axis for Hooke’s law practical?
Gradient for stiff spring?
Medium stiff?
Soft spring?
X axis- extension
Y axis- force
Steep gradient
Less steep gradient
Shallow gradient
Hooke’s law
Force applied to a spring and its extension are directly proportional, as long as its limit of proportionality isn’t exceeded
What happens to the force and extension relationship when it is beyond the limit of proportionality?
Extension of spring is no longer proportional to applied force
