P9: Forces And Their Effects Flashcards
(17 cards)
What is a force?
A push or pull acting on an object due to an interaction with another object.
What are the two categories that all forces can be split into?
- Contact forces (objects touching)
- Non-contact forces (objects separated)
Give three examples of contact forces?
- Friction
- Air resistance
- Tension
Give three examples of non-contact forces?
- Gravitational forces
- Electrostatic forces
- Magnetic forces
Is force a vector or a scalar quantity? Why?
• Vector
• It has both magnitude and direction
What is a scalar quantity?
• A quantity that only has a magnitude
• A quantity that isn’t direction dependent
What is a vector quantity?
A quantity that has both magnitude and direction.
Give three examples of vector quantities?
- Velocity
- Displacement
- Force
Give examples of scalar quantities?
• Temperature
• Time
• Mass
• Speed
• Distance
• Energy
How are vectors represented?
• Vector arrows
• Length indicates magnitude
• Arrow indicates direction
How can you calculate the resultant magnitude and direction of forces using a scale drawing?
• Draw the component forces as scaled arrows, joined tip-to-tail
• Draw a line connecting the two open ends.
• Measure the length of this line and convert into the magnitude.
• Measure the angle between the resultant line and the vertical/horizontal to find the direction.
What is an alternative name for the turning effect of a force?
A moment.
What distance measurement is used when calculating a moment?
The perpendicular distance from the pivot to the line of action of the force.
If an object is in equilibrium, what can be said about the moments acting on the object?
The clockwise moments are equal to the anticlockwise moments.
How do levers make use of moments?
They increase the perpendicular distance of the force from the pivot, so decrease the force needed to produce the same moment.
How are levers used to decrease the force required to lift something?
Levers use a pivot point and the concept of moments to reduce the force. The further you are away from the pivot point, the less force you need to lift the object up.
How does lubricating levers/gears improve efficiency?
There is less resistance; less energy is wasted/dissipated (as heat) overcoming frictional forces.
