P10 Flashcards
What does Newtons second law state
-Resultant force (F) is = to mass x acceleration
-inversely proportional to the mass of the object
Equation for newtons second law
F=ma
Resultant force = mass x acceleration
What is friction
force that resists the sliding or rolling of one solid object over another
What can you use to reduce the friction between surfaces
Lubricant
What is the most important factor when reducing drag
Keeping the shape of the object stream lined
What is drag
The force that acts in the opposite direction to the movement of the object
Why does a falling object accelerate
The force of gravity is much more than the frictional force
Why do you gradually slow down when you are falling down
Because the friction increases
What does it mean by a terminal velocity
When something has reached it’s maximum speed and starts to fall at a steady speed
What does terminal velocity depend on
Shape and area of the object
How does an object have a lower terminal velocity
If it has a larger surface area
What does stopping distance depend on
Thinking distance + braking distance
3 things effecting braking distance
- mass of vehicle
- speed of vehicle
- state of vehicle brakes
3 things effecting thinking distance
- levels of alertness
- drug / alcohole in system
- distractions (phone)
What is momentum
The mass and velocity of a moving object (Vector quantity)
Equation for momentum
Momentum (kg m/s) = mass (kg) x velocity (m/s)
What is conservation of momentum
When the total momentum before an event is the same momentum after an event
Equation for spring constant
Force = spring constant x extension
F = ke
What does the spring constant depend on
The material you are stretching
Inertia
The tendancy of sn object to stay at rest or to continue in uniform motion e.g moving at constant velocity
Inertial mass=
Force/acceleration
What happens to an objects acceleration when the fresultant force increases?
Acceleration increases as well
When does velocity increase?
If the resultant force is in the same direction
When does velocity decrease?
When resultant force is opposite to the velocity
What happens to an object acted on only by gravity?
Accelerates at 10m/s^2
Thinking distance:
Distance travelled by the vehicle in the time it takes the driver to react
What opposes the driving force of a vehicle?
Friction and air resistance
What increases braking distance?
High speed, poor weather, poor vehicle maintainance, poor reaction time
Momentum in a closed system:
Before and event is equal to after an event
Example of momentum
Skateboard going the opposite way from you
How is an object elastic?
If it returns to its original shape when the forces deforming it are removed
Stretch tests (pg 130 kerboodle)
1) the spring to be tested is clamped at its upper end. An empty weight hanger is attached to keep it straight
2) the length of the spring is measured using a metre ruler
3) the weight hung is increase by adding one at a time
4) length of the spring is measured each time a weight is added. Should be measured from the same points each time for accurate results
How is the weight on the string directly proprtional?
The spring gives a straight line through the origin
Hooke’s law: (limit of proportionality)
The extension of a spring is directly proportional to the force applied, as long as its limit is not exceeded
