p5 forces Flashcards
what has made the analysis of movement possible?
artificial limbs
what do scalar quantities have?
magnitude (size) only
what is a contact force?
a force acting on two objects that are physically touching
what do vector quantities have?
magnitude and direction
what and how can vectors be represented by?
an arrow
- the length represents the magnitude
- the direction also represents the direction of the vector
what is a non contact force?
a force acting on two objects that are not physically touching
examples of contact forces?
friction
air resistance
tension
normal contact force
examples of non contact forces?
gravitational force
electrostatic force
magnetic force
an example of forces acting on the earth and the sun?
they’re attracted to each other by a gravitational force, this is non contact as there is an equal and opposite force of attraction felt by both the earth and sun
an example on forces acting on a chair?
the chair exerts a downwards force onto earth called weight. while the earth exerts an equal and opposite force back onto the chair
what is weight?
the force acting on an object due to gravity. the force of gravity close to the earth is due to the gravitational field around the earth
what does the weight of an object depend on?
the gravitational field strength at the point where the object is
what is the ‘centre of mass’?
the weight of an object acting at a single point
what is the mass of an object directly proportional to?
the weight of an object
what is the weight of an object measured by?
newtonmeter
what is a resultant force?
a single force which replaces all of the forces acting on an object. this force has the same effect as all the forces that its replacing acting together
examples of forces acting on a moving car?
1) driving force, moving the car forwards
2) friction, dragging the car back
3) weight, acting downwards onto the ground
4) normal contact force, pushing the car up over the ground
examples of forces acting on a sky diver?
1) weight, pulling the diver down to the ground
2) drag, the air resistance pushing the diver upwards
what can a single force be resolved into?
two components acting at right angles to each other. the two component forces have the same effect as the single force
what causes an object to be at equilibrium?
when all the forces acting on an object combine to give a resultant force of 0
how can a scale diagram show that an object is at equilibrium?
the tip of the last force you draw should end where the tail of the fist force you draw begins. (eg three forces drawn should make a triangle)
how to find the missing force of an object which is at equilibrium?
join the two forces that you DO know tip to tail and join the end of the last force line to the start of the first one. this line is the missing force so you can measure it’s size and direction
how to split a single force into it’s horizontal and vertical components?
draw the force line on a scale grid. draw a horizontal arrow from the bottom end of the force and a vertical arrow to the top end of the force to form a right angled triangle
what causes work to be done on an object?
when a force causes an object to be moved through a distance. so force does work on an object when the force causes a displacement of the object