Topic 2 - motion and forces Flashcards
Vector
a vector quantity has both magnitude (size) and
specific direction
Scalar
a scalar quantity has magnitude (size) but no
specific direction
Examples of scalar quantities
Temperature
mass
time
energy
speed
distance
Examples of vector quantities
velocity
displacement
force
weight
acceleration
momentum
What is velocity?
Speed in a stated direction
How can a vector quantity be represented?
Vector arrows (length of arrow = magnitude).
Average speed
Average speed = distance ➗ time
(m/s) (m) (s)
average acceleration of an object
acceleration = change in time ➗ time taken
(m/s2) (m/s) (s)
equation for velocity (with a displacement)
v − u = 2× a× x
On a distance/time graph, what value does the gradient represent?
the speed
How can you calculate the speed at a given time from a distance time graph for an accelerating object?
- draw a tangent to the curve at the required time
- calculate the gradient of the tangent
On a displacement/time graph, what value does the gradient represent?
the velocity
How can the distance travelled by an object be calculated from a velocity-time graph?
It is equal to the area under the graph
On a velocity-time graph, what does the gradient of the graph represent?
The acceleration
typical value for the speed of sound
330 m/s
typical value for human walking speed
1.5 m/s
typical value for human running speed
3 m/s
typical value for human cycling speed
6 m/s
approximate value for the acceleration of an object in free fall under gravity near the earth’s surface
10 m/s^2
resultant force
the single force that is equivalent to all the other forces acting on a given object
Newtons first law for a stationary object
If the resultant force on a stationary object is zero, the object will remain at rest
Newtons first law for a moving object
If the resultant force on a moving object is zero, the object will remain the same at a constant velocity. (same speed, same direction).
Newtons second law
Resultant Force = Mass x Force
F=MA
Newton’s second law (in word)
An object’s acceleration is directly proportional to the resultant force acting on it and inversely proportional to its mass.
Weight?
The force that acts on an object due to gravity and the object’s mass
Weight equation
weight = mass x gravitational field strength
What can be used to measure an object’s weight?
A calibrated spring-balance or newton-metre
