KIN 320 Exam 1

Where is our center of mass normally?

Little higher than 50% of our height

Newtons 3rd Law

Law of action-reaction; every force has an equal and opposite force

GRF

the force of the ground pushing back up on you

Static equilibrium

Sum of forces = 0

Statics

Object at rest OR moving at a constant velocity

Dynamics

Objects in accelerated motion

Kinetics

Motion with the associated forces; force, impulse, gravity, etc.

Kinematics

Motion without the associated forces; speed, time, distance, etc.

Pressure equation

P=F/A

Pressure

Force per unit area; N/m² or Pascal (Pa)

Center of pressure

Point of force application

Normal force

Perpendicular to the two objects in contact

Parallel

Friction force is one

Magnitude

Product of the coefficient of friction and the normal ground reaction force (R)

Net (resultant) force

derived from the vector composition of all the acting forces; determines the net effect of all acting forces on a body; sum of all external forces acting on one object

Vector composition

Process of determining a single vector for two or more vectors by vector addition

Vector resolution

An operation that replaces a single vector with two perpendicular vectors such that the vector composition of the two perpendicular vectors yields the original vector

Newton’s 1st law

Law of inertia; an object in motion stays in motion

Inertia

Resistance of an object to changing motion

Momentum

Quantity of motion possessed by a body; measured as the product of a body’s mass and its velocity (M = mv)

Principle of conservation of momentum

In the absence of external forces, the total momentum of a given system remains constant; M1 = M2

Conservation of momentum

If velocity of one object in the system increases, velocity of another object decreased to conserve momentum

Impact

A collision characterized by the exchange of a large force during a small time interval

What happened during impact?

Described by the coefficient of restitution; serves as an index of elasticity for colliding bodies (e)

Coefficient of restitution (e)

Velocity of separation/velocity of approach

Velocity of separation

Difference between the post impact velocities of two colliding objects

Velocity of approach

Difference between the pre impact velocities of two colliding objects

Perfectly elastic impact

Speed of system conserved; e = 1

Perfectly plastic impact

Total loss of system speed; e = 0

Acceleration

the rate of change in velocity; a = change in velocity/time

Projectile

a body in free fall that is subject only to gravity and air resistance

Newton’s 2nd Law

law of acceleration; F = ma

Impulse

The product of a force and the time interval over which the force acts; causes change in momentum because it changes velocity

Projection speed

the magnitude of projetion velocity

instantaneous velocity

determines the ultimate horizontal displacement of the shot

relative projection height

the difference between projection height and landin height

Factors influencing projectile trajectory

projection speed, relative projection height, projection angle

1 radian

The angular distance covered when the arc length equals the radius; 57.3 degrees

Angular displacement

A change in angular position; the angle between final and initial angular position

Angular distance

Sum of all angular changes

Angular speed

Angular distance/time

Angular velocity

Rate of change in angular position; w