GEN PHYS 1 | WW1 Reviewer

True Value

the actual, exact value of the quantity measured (usually unknown)

Measured Value

the value obtained from the experiment or instrument

Absolute Error

the difference between the measured value and true value

Absolute Error Formula

∆x = |x_measured - x_true|

Relative Error

the ratio of the absolute error to the true value, often expressed as a percentage

Relative Error Formula

∆x/x_true

Systematic Errors

• consistent errors caused by faulty equipment or experimental design

• affects accuracy

• instruments must be recalibrated and techniques must be corrected

• has known causes (human error, faulty equipment, problematic design)

Random Errors

• errors caused by unpredictable fluctuations in measurements

• affects precision

• the experiment must be repeated several times and the average results must be used

• accidental

Addition of Errors

1. Add the measured values

2. Add the absolute errors

Multiplying of Measured Quantities

1. Multiply Quantities

2. Add relative errors

3. Multiply relative to product to get absolute error.

Exact Numbers

those values that are known exactly

Inexact Numbers

values with uncertainty

Accuracy

closeness of a measured value to its standard

Precision

closeness of individual measurements with each other

Projectile Motion

• object has initial velocity

• caused by external force

• travels freely due to gravity while neglecting other external forces (e.g. drag and friction)

• combines horizontal and vertical motion, which are independent of each other

Trajectory

path projectiles take under action of gravity, parabolic in nature

Airtime

time a projectile takes to complete trajectory

Maximum Height

highest vertical displacement

Range

horizontal distance traveled

Horizontal Motion is Projectile Motion

The projectile has constant horizontal velocity as there is no external force acting on it. This means its initial velocity is equal to the final velocity.

Vertical Motion in Projectile Motion

the projectile has constant vertical acceleration as gravity is constantly pulling the object downwards

Projectile Motion Cases

1. Launched horizontally

2. Launched at an Angle

Launched Horizontally Case

vertical component is free-fall motion, with the initial velocity always at 0 m/s as it launches at an angle of 0º

Launched at an Angle Case

vertical component is free-fall motion, with the initial velocity always upwards until it reaches its maximum height

Dynamics

study of the cause of motion

Force

• push and pull on an object

• interaction between two objects or between an object and its environment

Contact Forces

physical contact between two objects

Non-contact Forces

forces that act through empty space

Normal Force (N or F_N)

• force exerted on an object by any surface with which it is in contact

• perpendicular to surface

Friction (f)

• a force exerted on object that acts parallel to surface but opposite to the direction of the force

Tension Force (T)

• pulling force by string or cord that suspends an object in the air

Weight (W) Formula

Let

• m = mass

• g = force of gravity

W=mg

First Law of Motion

A body at rest remains at rest or if in motion, remains in motion with a constant velocity, unless acted on by an external force.

Inertia

A property depending on mass. As the mass increases, the inertia also increases.

Second Law of Motion

The acceleration of an object is in the same direction as the force exerted on the object. This force is equal to the product of the mass of the object and its acceleration.

F=ma

Third Law of Motion

If object A exerts force on object B, then object B exerts a force on object A that is equal in magnitude but opposite in direction.

Free Body Diagram

• systematic representation of all forces on an object

• denoted by arrows and symbols

• size indicates magnitude

• direction of arrows indicates direction of magnitude

Static Friction

occurs when there is no relative motion by resisting the object sliding

Kinetic Friction

occurs when surfaces slide past one another

Coefficient of friction (u)

constant that is determined based on the material surface