Mechanics Flashcards
What is the word equation for speed?
Speed = distance / time
What is the symbol equation for speed?
v = d / t
What is the equation for velocity?
v = s / t
velocity = changed in DISPLACEMENT / time
What is a scalar quantity?
A quantity with magnitude ONLY
What is a vector quantity?
A quantity with BOTH magnitude AND direction
What is velocity measured in?
ms^-1
Define acceleration?
The rate of change of velocity
What is the equation for acceleration?
a = (v-u) / t
acceleration = change in velocity / time
What is acceleration measured in?
ms^-2
How is average speed calculated?
Total distance / total time
What is instantaneous speed?
The speed at any particular instant in time of a journey
How can instantaneous speed be found?
The gradient of a distance - time graph
What is the symbol used for displacement?
s
What is the symbol used for distance?
d
What is the symbol used for speed?
s
What is the symbol used for energy?
e or W
What does the gradient of a displacement - time graph tell you?
The velocity
How can acceleration be found from a velocity - time graph?
The gradient
Other than acceleration, what can a velocity time graph show you and how?
The displacemnent - the area underneath the graph
Name the SUVAT equation that does NOT have s in it?
v = u + at
How can s = ut + 1/2at^2 be derived?
Combining the equations:
v = u + at
s = 1/2 (v+u) t
s= 1/2(2ut + at^2)
s = ut + 1/2at^2
How can v = u + at be derived?
A= (v-u) / t
Rearrange to find v
Name the SUVAT equation that does NOT have v in it?
s = ut + 1/2at^2
Name the SUVAT equation that does NOT have t in it?
v^2 = u^2 + 2as
Name the SUVAT equation that does not have a in it?
s = 1/2(u + v)t
What is needed for SUVAT equations to work?
A constant acceleration
How many values of SUVAT are needed to find another?
3
If an object is being thrown and has left the hand, which direction is the acceleration happening?
The reverse direction ( the ball is not going to speed up after it has left your hand)
How must diagram be drawn when showing forces?
All the forces must be joined tip to tail
What is a vector?
A quantity with magnitude AND direction
What do we use to represent vectors?
Arrows. The direction is the direction and the length is the magnitude
What must always be true about the reaction force?
It must be perpendicular to the surface it is acting on
What must always be true about a frictional force?
It must be parallel to the surface it is acting on
Why would two objects that have 0 vertical velocity fall at the same rate, even if the horizontal velocities were different?
Because the only force acting on both objects is the force due to gravity (ignoring air resistance)
What is a moment?
A turning effect on an object around a pivot due to a force being applied
How do you calculate moments?
Moment = force x perpendicular distance
What two things MUST be true for an object to be in equilibrium?
- The forces are balanced
- The net moment is zero
What is the centre of gravity?
The point at which all the weight of an object can be considered to act
How can you represent forces that do not all act from the same point on an object?
Using a line
What is a freebody diagram?
A diagram where an object is shown with all the forces acting on it, ignoring other objects around it
What is Newton’s First Law?
An object will remain at rest or at constant velocity unless an unbalanced force acts on it
What is newton’s Second Law?
If an unbalanced force acts on an object its velocity/momentum will change
What equation goes with Newton’s Second Law?
(net) force = mass x acceleration
What is Newton’s Third Law?
When a force acts between 2 objects, it will have equal magnitude on both objects but in opposite direction
Every action has an equal and opposite reaction
