P8: Forces Flashcards
What is a vector quantity?
They have a magnitude and direction
Give examples of vector quantities?
Force, velocity, displacement, acceleration, momentum
What is a scalar quantity?
They only have a magnitude and no direction
What are some examples of scalar quantities?
Speed, distance, mass, temperature, time
What is velocity and what is speed?
Velocity - vector
Speed - scalar
What is distance?
How far an object moved. It is scalar. It doesn’t involve direction
What is displacement?
Distance and direction in a straight line from an objects starting point to it’s finishing point. Vector.
What is a contact force?
When two objects have to be touching for a force to act.
E.g. friction, air resistance, tension in ropes, normal contact force
What is a non-contact force?
If the objects do not need to be touching for the force to act.
E.g. magnetic force, gravitational force, electrostatic force
What is an interaction pair?
A pair of forces that are equal and opposite and act on two interacting objects.
How does an object start moving from rest?
The forces acting on it are unequal.
How do you work out resultant forces?
The greater force - the smaller force
What happens if the resultant force is 0?
if the object is at rest, it stays stationary
if the object is moving, it keeps moving with the same speed and in the same direction
How do you work out the moment?
M = Fd
What does using a lever do?
Less force is needed.
What will happen when a force is transmitted to a larger gear?
A bigger moment
Compare a larger gear and a smaller gear?
The larger gear will turn slower than the smaller gear.
What is the condition for forces to balance?
Anti-clockwise moment = clock-wise moment
What is a low gear?
Gives low speed and high turning effect.
What is a high gear?
Gives high speed and low turning effect.
What does freely suspended mean?
If it returns to its equilibrium position after the turning force is taken away.
Explain why the vehicle does not roll over on this angled embankment.
The centre of mass falls inside its wheel base therefore there is no resultant / clockwise moment.
Explain why the force of the bottle opener on the cap is much larger than the force applied to the bottle opener by the person opening the bottle.
Bottle opener is a force multiplier. The effort acts further from the pivot than the force of the bottle opener on the top so the force of the bottle opener on the top is greater than the effort.
Explain why the force needed to lift the wheelbarrow’s legs off the ground is much less than the combined weight of the sand and the wheelbarrow.
The distance from the wheel axle to force is much greater than the distance from the axle to the centre of mass. The weight of sand and wheelbarrow causes a moment about wheel axle.(1)
To lift the wheelbarrow legs off the ground, the force must create a greater moment about the wheel axle.(1)
Because the distance from the wheel axle to force is much greater than the distance from axle to centre of mass, the force is less than the weight to give greater moment than the weight.(1)
