P8 Forces In Balance Flashcards
What is a vector?
A quantity with a given direction and magnitude
What is a scalar?
A quantity with a given magnitude but not direction.
What is displacement?
A distance without a change in direction
If someone starts a walk from a certain point and finishes at the same point, what is their total displacement?
0
Sort ACCELERATION, MASS, SPEED, TIME, FORCE, DISTANCE, ENERGY, POWER and WEIGHT into vector and scalar quantities
Vector:
- Acceleration,
- force,
- weight.
Scalar:
- Speed,
- mass,
- time,
- energy,
- distance,
- power.
What is the difference between speed and velocity?
Speed has magnitude but no given direction whilst velocity is speed with magnitude and direction.
Vector or scalar:
The body had a mass of 45kg
Scalar
Vector or scalar:
The weight of the body is due to gravity so moves downwards
Vector
Vector or scalar:
The speed of the car was constant as it circled the roundabout
Scalar
Scalar or vector:
The magnetic field lines act from the N Pole to the S Pole
Vector
A force can cause an object to:
- Change shape,
- change its velocity,
- change its state of rest (start moving).
Sort magnetic, friction, air resistance, thrust, nuclear, electrostatic, tension and gravitational into contact and non-contact forces
Contact:
- Air resistance,
- tension,
- friction,
- thrust.
Non-contact:
- Magnetic,
- nuclear,
- electrostatic,
- gravitational.
What is Newton’s third law of motion?
When two objects interact with eachother they exert opposite and equal forces on eachother.
3 examples of Newton’s third law:
- When a swimmer pushes their legs off of a wall in the swimming pool,
- when an object is lying on a table,
- when someone is standing on a surface.
If two roller stakers pulled a rope in opposite directions, what would happen and why?
Their legs would crash into eachother because there would not be enough friction to stop the reaction force.
What is friction?
Friction is the force exerted by a surface against an object when it moves across it.
Name all the forces on a moving car
Friction, gravity, drag, thrust, reaction force.
If a car is moving and two opposite and equal forces act on it, what will happen?
The car will continue travelling at the same speed
Difference between balanced and unbalanced force
Balanced force is when two opposite forces are equal and the resultant force is 0 though unbalanced is when one is greater than the other and resultant force is not 0.
What is Newton’s first law of motion?
If the resultant force on an object is 0, all forces are said to be balanced
What is the main thing that stabilises or destabilises an object?
Centre of mass
How do you find the centre of mass in a regular shaped object?
Draw all the lines of symmetry and where they cross is the centre of mass.
How do you find the centre of mass in an irregular shaped object?
Hang the object from a plumb line and draw a line straight down in the direction of it. Do the same thing at another point. Where the lines intersect is the centre of mass.
What is centre of mass?
The point in an object where the mass is most evenly distributed from.
If the line of action in a vehicle moves outside the base, what will happen?
It will topple over
What two things can be done to an object to make it more stable?
Make the object shorter (lower centre of mass) and wider (line of action will stay more easily within the base)
If two forces are acting from a certain point within a 90’ angle, what can be done to find the size and direction of the resultant force?
- Choose a scale for cm:N,
- draw out the two forces using the scale,
- calculate the angle between the forces,
- draw the angle which is co-interior to the one already calculated along the width of the parallelogram,
- draw a parallel line at the top of the parallelogram,
- draw an arrow from the first angle to the intersection between the two lines,
- measure the length of the arrow and convert this into newtons.
How do you calculate the resolution of forces?
- Pick a scale for cm:N,
- draw the force acting down on the object,
- draw a line parallel to the slope the object is resting on,
- draw a perpendicular line from the parallel line to force acting on the object,
- measure the parallel line from both points and convert to newtons.
