Linear, Angular and Projectile Motion Flashcards
What’s linear motion
A motion in a straight or a curved line with all body parts moving in the same direction at the same speed i.e a javelin moves in a straight line
What causes linear motion
Direct force being applied to an objects centre of mass
What descriptors are linked to linear motion (10)
• Distance
• Displacement
• Speed
• Velocity
• Acceleration
• Deceleration
• Mass
• Weight
• Inertia
• Momentum
What are the two categories of descriptors linked to linear motion
Scalar and Vector
What are scalar quantities
Quantities described in terms of size or magnitude
Name the scalar quantities linked to linear motion
• Distance
• Speed
• Mass
• Inertia
What are vector quantities
Quantities described in terms of size and direction
Name the vector quantities linked to linear motion
• Displacement
• Velocity
• Acceleration
• Deceleration
• Weight
• Momentum
What are distance and displacement
Measurements that are used to describe a body’s motion
What’s distance
• The length of the path a body follows when moving to a point and always has a positive value
• E.g. a 400m runner runs 400m
What’s displacement
• The length of a straight line joining the start and finish points and is the shortest distance between two points
• E.g. the displacement of a 400m is 0 because the start/finish is the same and the displacement of a 200m is the number of metres the crow flies across the track from start to finish
What’s speed
The rate of change of position
What’s the equation for speed
Speed (m/s-1) = Distance covered (m)
——————————-
Time taken (s)
What’s velocity
The rate of change of position with reference to direction. This means it’s a more precise description of motion
What’s the equation for velocity
Velocity (m/s-1) = Displacement (m)
——————————-
Time taken (s)
Define acceleration and deceleration
The rate of change of velocity
What’s the equation for acceleration (or deceleration)
Acceleration (m/s2) = Final V - Initial V (m/s)
——————————-
Time taken (s)
What’s angular motion
• Movement around a fixed point (eg. a gymnast performing a somersault) that occurs when a force is applied outside the centre of mass
• An off-centre force is referred to as eccentric force (torque)
What’s torque
The rotational force of a body that causes an object to turn around its axis of rotation
What are the three axes
• Frontal (side to side)
• Sagittal (front to back)
• Vertical (top to bottom)
What descriptors are linked to angular motion
• Torque
• Angular velocity
• Inertia
• Angular momentum
What’s angular velocity
Refers to the angular displacement that’s covered in a certain time
What’s the equation for angular velocity
Angular velocity = Angular displacement (rad)
(Rad/s) ————————————-
Time taken (s)
What’s inertia and moment of inertia
The resistance of change of linear motion, moment of inertia is therefore resistance of a body to angular motion, and depends on two factors
What two factors does moment of inertia depend on
• Mass of the body/object
• Distribution of mass from the axis of rotation
How does mass of the body/object affect moment of inertia
The greater the mass, the greater the resistance to change and therefore the greater the moment of inertia
How does distribution of mass from the axis of rotation affect moment of inertia
The closer the mass is to the axis rotation, the easier it is to turn.
- Increasing distribution = increased moi
- Decreasing distribution = decreased moi
Provide an example on the effect of distribution of mass from the axis of rotation on moment of inertia
A somersault a straight position has a higher moment of inertia than the tucked somersault. In a straight position the distribution of the gymnasts mass is further away from the axis of rotation
What’s the equation for moment of inertia
Moi (kgm2) = mass (kg) X distribution of mass
from the axis (m2)
What’s angular momentum
Spin; it involves the object or body in motion around an axis
What two things does angular momentum depend on
• Moment of inertia
• Angular velocity
If moi increases, angular velocity decreases and vice versa
What’s the equation for angular momentum
Angular momentum = moi X angular velocity
(Kgm2 rad/s) (Kgm2) (rad/s)
Outline the conservation of angular momentum
Angular momentum is conserved unless an external torque acts upon it
Provide an example of the conservation of angular momentum
The moment of inertia when a break dancer in the Olympics spins on their head can be manipulated by bringing in their arms and legs closer to the axis of rotation, resulting in a smaller moment of inertia and a large angular momentum
