Force Flashcards
What is Newton’s 1st Law?
-The velocity of an object will not change unless a resultant force acts on it
-It will either be travelling at a constant speed or is stationary, if it has no resultant force
-It will accelerate in the direction of the resultant force
-F=ma if F = 0, then a = 0
What is Newton’s 2nd Law?
-F=ma
-More force = More Acceleration
-More mass = Less Acceleration
What is Galileo’s theory?
-All objects fall at the same rate if you ignore air resistance
What is Newton’s 3rd Law?
-If object A exerts a force on object B, then object B exerts an equal but opposite force back on A
-Applies in all situations and to all types of force, however they have to be the same type
What is fluid friction or drag?
-The force depends on the viscosity of the fluid
-It increases as speed increases
-The larger the area of the object, the greater its resistance
-A projectile is slowed by air resistance
What is friction?
-A force which opposes motion
-Always acts in the opposite direction to the motion of the object
-They can never speed things up or start moving something
-Convert kinetic energy into heat and sound
What is terminal velocity?
-When the driving force stays the same all the time, and the frictional force is equal
-The acceleration and resultant force is 0
What is the conservation of momentum?
-Assuming no external forces act
-Total momentum before equals total momentum after
-Forward momentum equals backwards momentum
How does Newton’s Second Law explain momentum?
-The rate of change of momentum of an object is directly proportional to the resultant force which acts upon it
How does Newton’s Third Law explain momentum?
-If object A collides with object B and exerts a force on B for a time, newton’s third law says that the object B will also exert a -force on A for the same time
-If you add the two it will equal 0 which shows its conserved
What is work done?
-The amount of energy transferred from one form to another when a force causes a movement
-Is the increase in potential energy not it total potential energy
What are 4 examples of Work done?
-Lifting a box: Work is done against gravity, and is converted to gpe
-Pushing a chair across a floor: Work done against friction, and is converted to heat
-Pushing two magnetic north poles together: Work done against the magnetic force, and is converted to magnetic energy
-Stretching a spring: Work done against the stiffness of the spring, and is converted to elastic potential energy
What is a joule?
-One joule is the work done when a force of 1N moves an object through a distance of 1m
What is power?
-The rate of doing work, or the amount of energy transferred per second
-The watt is equal to Js^-1
What is a body’s mass?
-The mass of an object is the amount of matter in it
-The greater the object’s mass, the greater its resistance to a change in velocity
What is weight?
-The force experienced by a mass due to its gravitational field
What is the centre of gravity of an object?
-Is the single point that you can consider its whole weight to act through
-The object will always balance around this point
How can you find an objects centre of mass?
-A regular object is by symmetry
-An irregular object is by hanging it from a point and drawing a vertical line from it, using a plumb bob and then doing that in multiple point, the centre of gravity is the point in which the lines cross
How does the centre of gravity affect stability?
-An object will be stable with a low centre of gravity and a wide base
-An object will topple if a vertical line, line of action, downwards from the centre of gravity falls outside its base area, as its causing a moment/turning force around a pivot
What is a moment?
-The turning effect of a force and depends on its size and how far the force is applied from the turning point/axis of rotation
-The principle of moments states that for an object to be balanced, the sum of the clockwise moments will be equal to its anticlockwise moments
How does our body act as a lever?
-An effort force, muscles, acts against the load force, the weight of the arm, by means of a rigid object, the bone, rotating around a pivot, the joint
Why do things fall over?
-If the centre of gravity is to one side of a pivot then it will turn as there is no opposite force
-If the centre of gravity is on the pivot, then it won’t turn
