CP2 - Forces and Motion Flashcards
What is a scalar quantity?
A quantity with magnitude(size) only.
E.g. speed, time, energy, mass
What is a vector quantity?
A quantity with both size AND direction.
E.g. velocity, force, weight, acceleration
What is a resultant force?
An overall force acting on an object with 2 or more forces acting on it.
Add the forces together if they’re in the same direction, or take them away from each other if they are in different directions.
It can be balanced, if the forces are taken away and equal to 0.
What is Newton’s first law?
A moving object will continue to move at the same speed and direction unless an external force acts on it.
A stationary object will stay stationary unless an external force acts on it.
What is the centripetal force?
The resultant force that causes the object to change direction, staying in a circular path as it acts on the centre of the circle.
It depends on the mass and speed of the object, and on the radius of the circle.
What is Newton’s 2nd law?
The acceleration of an object depends on the force and mass of the object.
Acceleration is directly proportional to the force acting on the object, but inversely proportional to the mass of the object.
Can be written as:
Force (N) = mass (kg) x acceleration (m/s2)
Also:
Inertial mass = force ÷ acceleration produced
What is Newton’s 3rd law?
For every action (force) in nature there is an equal and opposite reaction.
This interaction can happen when:
Objects touch
At a distance, e.g. gravitational attraction
What are action-reaction forces?
2 forces acting on 2 interacting objects. The forces are always the SAME SIZE but in OPPOSITE DIRECTIONS, and they are always the SAME TYPE of force.
What is equilibrium?
When the action-reaction forces acting on object are the same size; nothing moves.
This is NOT the same as balanced forces (action-reaction forces act on different objects, balanced forces act on the same object).
What is momentum?
How hard it is to stop something moving.
How to calculate momentum?
Momentum (kg m/s) = velocity (m/s) x mass (kg)
How to calculate the change in momentum?
Force (N) = change in momentum / time (s)
(𝑚𝑣−𝑚𝑢)/𝑡
What is the conservation of momentum?
Momentum before collision = momentum after collision
How are forces of momentum reduced in cars?
Crumple zones
Crumple zones crumple up when a car hits something, increasing the amount of time the car takes to come to a stop, decreasing deceleration and the force on the car.
How are forces of momentum reduced in cars?
Seat belts
Seat belts stop you from going forward, increasing the time for you to come to a stop/.
