exam 1 physics

Science Notes on Quantities

In science, a quantity is defined as a property of an object or substance that can be measured or calculated from other measurements. Quantities are expressed as values, which consist of a numerical value and a unit of measurement. Here are some examples of quantities:

• 20 seconds

• 75 meters

• 10 m/s

Important Quantities in Physics

The following are some of the key quantities discussed in this course. You need to familiarize yourself with these details for your upcoming quiz. (This sheet cannot be used during the quiz.)

Fundamental and Derived Quantities

• The shaded boxes in the table that include mass, time, and length are termed fundamental quantities. These cannot be easily defined using other quantities. Other quantities like velocity, acceleration, and force are known as derived quantities since they are combinations of fundamental quantities.

Velocity and Acceleration

Velocity is defined as the distance an object travels per unit time. Mathematically, this is expressed as: [ \text{velocity} = \frac{\text{distance traveled}}{\text{time traveled}} ]

Acceleration quantifies how fast the velocity of an object is changing, whether the object is speeding up or slowing down. If an object's speed is constant, it is considered to have zero acceleration.

The formula for acceleration is: [ a = \frac{U_f - V_i}{t} ] Where:

• ( a ) is the acceleration,

• ( U_f ) is the final velocity,

• ( V_i ) is the initial velocity,

• ( t ) represents the time taken to change velocity.

Inertia and Newton's Laws

The property of an object to resist changes in its motion is known as inertia. Mass is a measure of an object's inertia. A large mass indicates a greater resistance to changes in motion. For example, it is harder to stop a moving train than a bicycle due to the train's larger mass, hence more inertia.

Newton's Second Law can be expressed as: [ \text{sum of the forces on the object} = \text{mass of the object} \times ext{acceleration} ] Written in variables, it looks like: [ F = ma ]This law explains how variations in force or mass will influence an object's acceleration.

Total Force and Motion

Understanding when the total force on an object is zero is crucial. Two scenarios can lead to a net force of zero:

1. Multiple forces act on the object and cancel each other out.

2. No forces are acting on the object at all.

When the net force is zero, the object cannot experience acceleration; it may be stationary or moving at constant velocity.

Newton's First Law

Newton's First Law states that an object in motion will remain in motion at a constant speed and in a straight line, and an object at rest will remain at rest unless acted upon by an unbalanced force. This law reflects an important idea regarding inertia and motion.

Work and Energy

Work, defined as the force applied on an object multiplied by the distance the object moves in the direction of the force, is represented by: [ W = F \times d ]

• Here, force is measured in Newtons (N) and distance in meters (m), resulting in units of work expressed as Joules (J).

• Energy is the capacity to do work, with different forms including kinetic energy (related to motion) and potential energy (related to position).

Waves and Oscillations

• Periodic Oscillations lead to a discussion on waves. A wave transports energy without moving matter.

• The wavelength (\( ext{\lambda}) or \( ext{W}) ) is the distance between wave crests, while the amplitude measures the maximum displacement from equilibrium.

Wave Properties and Superposition

Waves can overlap, showcasing the principle of superposition:

• Constructive interference occurs when crest meets crest, resulting in increased amplitude.

• Destructive interference happens when crest meets trough, effectively cancelling the wave.

Sound Waves

Sound is generated by longitudinal pressure waves, requiring a medium such as air to propagate. Sound travels quicker in liquids and solids due to closer molecular proximity, enhancing responsiveness.