TOPIC 2 - FORCES AND MOTIONS Flashcards
What is a scalar quantity?
Has magnitude (size) but no direction
What is a vector quantity?
Has magnitude and direction
What is acceleration?
The change in velocity
What is acceleration in free fall on Earth?
10m/s
Speed equation
distance/time
Acceleration equation
change in v/time
Equation linking acceleration and distance
v^2-u^2=2 x acceleration x distance
What is Newton’s 1st law?
Where the resultant force is 0, the body moves at constant velocity or is at rest. When there is a resultant force, the speed and or direction of the body changes (accelerates)
What is Newton’s 2nd law?
Acceleration depends on
1.the size of the force (the larger the force, the larger the accel.)
2.the mass of the object (more mass = less accel.)
F=ma, hence acceleration is inversely proportional to mass
What is Newton’s 3rd law?
When 2 objects interact, action-reaction forces act (they are same size and same type of force but opposite direction). But forces have different effects if objects are different mass.
What is the different between mass and weight?
Mass is quantity of matter, weight is a measure of pull of gravity (a force).
Equation for weight
weight(N) = mass(kg) x gravitationa forcel(N/kg)
What is centripetal force?
any force is causing object to move in a circle, acting towards a circle and causes acceleration
What affects centripetal force?
- Radius of circle (smaller radius=more acceleration)
- Speed of object (more speed=more acceleration)
- Mass (more massive=needs larger force)
What is inertial mass?
how difficult it is to change velocity of an object. mass=f/a.
How is inertial mass related to acceleration?
it is inversely proportional to acceleration; larger mass = small acceleration
What is momentum?
tendency of an object to keep moving and how hard it is to stop moving
What makes momentum of an object to change?
- object accelerates/decelerates
- changes direction
- mass changes
What happens to momentum in a collision?
- if objects collide and move in opposite directions object will have different velocity depending on its mass and initial momentum
- if objects move in the same direction, they will have combined mass and velocity
- When 2 objects collide one object speeds up (gaining momentum) one object slows down (losing momentum)
What is conservation of momentum?
Total momentum before = total after: momentum conserved in collision (only transferred between objects)
Why is momentum not always totally conserved?
Because external forces could act (e.g. friction)
momentum equation
momentum = mass x velocity
equation linking momentum and force
mv-mu/time
how to calculate stopping distance
thinking distance + braking distance
thinking distance factors
- speed
- reaction time
- distractions
- drugs
braking distance factors
- speed
- mass
- state of brakes
- weather
- road conditions
why is large deceleration on the road dangerous?
- f=ma means less acceleration=more force meaning more injury likeliness
- large change in momentum = more force meaning more injury likeliness
how to calculate braking distance
braking force x braking distance = 1/2 x mass x velocity^2
