P8: forces in balance Flashcards
What is displacement?
A given Distance without change of direction.
What is a vector quantity?
A physical quantity witch has magnitude and direction.
What does a scalar quantity have?
A scalar quantity has a magnitude but no direction
What can a vector quantity be represented by?
An arrow in the direction of the vector and of length in proportion to the magnitude of a vector.
contact forces definition
If two objects must touch each other to interact.
What is Newton’s third law of motion?
When two objects interact with each other, hey exert equal and opposite forces on to each other.
What is the unit of force?
Newtons
Can forces change the shape of an object or change its motion or state if rest?
YES
What happens when two objects interact?
They always exert equal and opposite forces onto each other.
What is Newton’s first low of motion?
If forces acting on an object are balanced the resultant force is 0. The object will stay stationary if at a rest
- the object (if moving) will keep moving at the same speed and in the sane direction.
What does it mean when the resultant force is not 0?
The forces acting on the object are not balanced.
What happens when the resultant force is greater or less than zero?
The speed or direction of the object will change.
What does the centre of mass mean?
The centre of gravity, where the most gravity on the object is(usually in the middle).
Where is the centre of mass of a uniform ruler?
At its mid point
When an object is freely suspended and it comes to rest, where is its centre of mass?
Directly underneath the point of suspension.
Where is the centre of mass in a symmetrical object?
Along the axis of symmetry.
What does equilibrium mean?
At a rest
Forces are balanced so constant spped could occur MUST CHECK
What is a parallelogram of two forces?
A scale diagram of two force vectors.
What is resultant force of a parallelogram?
The diagonal, it starts at the origin of the two forces.
Why is an object at a rest in equilibrium?
Because the resultant force is 0
What does resolving a force mean?
Finding the perpendicular components that have a resultant force equal to the force
What are forces?
Vector quantities because they have direction and magnitude(size)
What is a resultant force?
A single force with the same effect of all the original forces acting together.
How do you work out the resultant force?
You subtract the smaller force from the larger force if directly opposite.
What is magnitude?
No relation to distance or direction like the amount eg the size of an earthquake.
What is a constant velocity?
A constant speed in a constant direction. A constant velocity means motion in a straight line at a constant speed.
What is drag?
The forces that opposite the movement of an object.
How do you know if a force is contact or non-contact?
Non contact forces are usually linked with some sort of field.
Examples of contact forces:
Friction
Air resistance
Tension
Ect it is in CONTACT
What are a few types of non-contact forces?
Gravitational force
Magnetic force
Electrostatics
Nuclear force
What is the resistive force?
A force witch the direction is opposite to the velocity to the sum of the other forces.
What is a free body diagram?
A diagram where the object is signified usually by a dot or box.
What is a vector diagram?
Vector diagrams are simply diagrams that contain vectors. A vector is an arrow that represents a quantity with both magnitude and direction. The length of the arrow represents the magnitude (or size) of the quantity, and the direction of the arrow represents the direction.
What is a parallelogram of two forces!
A to scale diagram of 2 force vectors
Equilibrium
Resultant force =0
Forces acting on the object have NO overall turning effect.
Law of moments
The longer the lever the less force you need.
force Fx distance
Turning force newtons cm
Earths gravitational field?
Mass 100 g
Earth g=10 n/KG
Resolving?
Get it back to horizontal and vertical
