Mechanics 1 - Scalars, Vectors and Moments Flashcards
State two conditions for any object to be in equilibrium
Resultant force zero
Resultant moment about any point zero
State three vector quantities
Any 3 of the following:
Velocity
Acceleration
Force
Displacement
Weight
Momentum
State three scalar quantities
Any 3 of the following:
Speed
Distance
Mass
Energy
Power
Temperature
How can force vectors be arranged to show that an object has constant velocity?
- Vectors make a closed shape when rearranged (by scale drawing)
- Or resolve into components and show
- Total up forces = Total Down forces
- Total left forces = Total right forces
What is the difference between a vector quantity and a scalar quantity?
Vector has a direction
Scalar does not
What is meant by centre of mass?
The point in a body where the weight of the object appears to act
Also the resultant moment about this point = 0
Define the moment of a force
Product of the force and the perpendicular distance from the line of action of the force to the point
State the principle of moments
Sum of the clockwise moments about a point is equal to the sum of the anticlockwise moments for a system in equilibrium
Resolve F into its vertical and horizontal components…
FH = FcosØ
Fv = FsinØ
What mistake has been made in rearranging the vectors for a scale drawing?
6N vector has been translated (moved) but also rotated
Should be:
What are the steps in working out the resultant force using a tip-tail scale drawing?
- Set a scale
- Draw the horizontal or vertical vector first (if there is one)
- Move each vector in turn to the end of the previous one (DO NOT ROTATE THE VECTORS)
- Resultant vector goes from the very start to the very end
How is the balancing force different from the resultant force?
The balancing force brings the object into equilibrium so makes the resultant force = 0
For a scale drawing, it is the vector that closes the shape
If vectors are parallel they can be resolved by…
Adding or subtracting the values
If vectors are perpendicular they can be resolved by…
Making a right angled triangle and using trigonometry and pythagoras
What is wrong with this?
Vectors of different types can’t be combined
(Here, force and velocity cannot be combined)