5. Forces Flashcards
What is a scalar?
Quantities that are fully described by magnitude or size
What are vectors?
Quantities that are fully described by both a magnitude and direction
What is distance?
A scalar quantity that refers to ‘how much ground an object has covered’
What is displacement?
A vector quantity that refers to ‘how far out of place an object is’
What is magnitude?
Size
How can vectors be drawn?
Using arrows
Is time a vector or scalar quantity?
scalar
Is force a vector or scalar quantity?
Vector
Is friction a vector or scalar quantity?
Vector
Is weight a vector or scalar quantity?
Vector
Is displacement a vector or scalar quantity?
Vector
Is distance a vector or scalar quantity?
Scalar
Is density a vector or scalar quantity?
Scalar
Is energy a vector or scalar quantity?
Scalar
Is frequency a vector or scalar quantity?
Scalar
Is mass a vector or scalar quantity?
Scalar
Is power a vector or scalar quantity?
Scalar
Is voltage a vector or scalar quantity?
Scalar
Is volume a vector or scalar quantity?
Scalar
What is the gradient on a distance-time graph?
Velocity
What is the gradient on a velocity-time graph?
Acceleration
What is the area under a velocity-time graph?
The distance
What is acceleration?
When an object speeds up or changes direction
What is the total area underneath a velocity-time graph?
The total distance travelled
What is the unit of force?
Newtons, N
Examples of contact forces?
- Friction
- Air / Water resistance (drag)
- Normal contact (reaction)
- Tension
- Upthrust
Examples of non-contact forces?
- Gravity
- Magnetic
- Electrostatic
What happens when the resultant force on an object is zero?
The object remains stationary or continues to move at a constant speed and in the same direction.
What is Newton’s 1st law of motion?
An object will remain at rest or at a constant velocity unless there is a resultant force acting on it.
What is Newton’s 2nd law of motion?
The acceleration of an object is directly proportional to the resultant force and inversely proportional to the objects mass.
What is Newton’s 3rd law of motion?
If object A exerts a force on object B, then object B exerts a force on object A which is equal and opposite.
What is thinking distance proportional to?
Speed
What is braking distance proportional to?
Speed2
What is thinking distance?
The distance travelled during reaction time.
What is braking distance?
The distance travelled while the brakes are applied.
Why does thinking distance increase?
- the speed increases
* the reaction time increases eg. tiredness, distraction, taken drugs / alcohol
When does braking distance increase?
If the initial speed increases or if the size of deceleration is less.
Typical speed of walking?
1.5 m/s
Typical speed of running?
12 m/s
Typical speed of driving?
20 m/s
Typical speed of flying?
200 m/s
Speed of sound in air?
3x10 squared
Speed of light?
3x10 to the 8
What is the weight of an object?
The force of gravity on it
How to convert from Kg to N?
x10
When does an object reach constant velocity?
When the drag force is equal and opposite to its weight
What is terminal velocity?
When an object reaches a constant velocity because the drag force is equal and opposite to its weight
What happens to the drag force when an object is released in a fluid before its terminal velocity?
The drag force is less than its weight before it reachers terminal velocity
What happens to acceleration when an object is released in a fluid after its terminal velocity?
It is equal to zero
What happens to the resultant force on an object released in a fluid initially?
The resultant force is equal to its weight, initally
When an object is falling, what does it initially accelerate at?
10 m/s2
What are plastic objects?
Objects that do not regain their original shape when the forces deforming it are removed
What are elastic objects?
An object that regains its original shape when the forces deforming it are removed
It stores elastic potential energy when work is done on the object
Does an elastic collision lose kinetic energy?
No
What does Hooke’s law state?
That the extension of a spring is in direct proportion with the force applied to it
What is the spring extension?
New length - original length
What does hooke’s law only apply to?
Elastic materials
What happens to a spring if the force added on the spring is larger?
It not longer obeys hooke’s law and does not return to its original length
What is elastic limit?
The limit of proportionality (when hooke’s law no longer applies)
What is stopping distance?
Thinking distance + braking distance
