Force

Definition

Force is a push or a pull given by the interaction of one object with another.

There are two types of forces:

Contact Forces:Frictional ForceApplied ForceNormal Force

Air Resistance Force

Non-Contact Forces:Gravitational Force

Electrical ForceMagnetic Force

Applied Force

Force that is applied consciously

Pushing a desk

Frictional Force

Exerted by a surface on an object moving across it

Endless moving ball and Newton’s First Law

Gravity Force (Weight)

Force that massively large objects (Earth, moon, Sun) exert on every object on it

Weight = m x g

M = Mass

G, on Earth = 9.8 N/kg

Gravity

How Does Gravity Affect the Body?

Gravity is a key component in muscle development

Center of mass

Impact on Sports

Weight Lifting

Impact on Sports

Wrestling

Mass and Weight

What is Mass?

The amount of material/matter in a body.

The more matter there is the more it will weigh.

Mass stays the same.

Measured in Kilograms.

Greater mass = more weight.

What is Weight?

How hard gravity pulls on an object.

Weight changes.

Measured in Newton's.

Greater mass = more weight.

Instantaneous Velocity (The only difference between instantaneous speed and instantaneous velocity is that speed is a scalar and velocity is a vector).

The measure of velocity of an object at a particular moment.

Velocity is the rate at which an object changes its position

Velocity is speed with direction (vector)

Sometimes we want to be more precise about what is happening between the initial and final times in a problem.

Instantaneous velocity is the velocity at a specific instant in time. This can be different to the average velocity if the velocity isn't constant.

Instantaneous Acceleration Acceleration (change of velocity/time) at any given time. It is the

acceleration of a certain body (or particle) at any particular given or chosen instant.

An example would be if you had a car, in 1st gear there is more torque applied to the wheels so its acceleration is higher. Shifting to 2nd gear you are going faster, but your acceleration is less. Let's say you ended up spending 2 seconds in 1st gear, and went from 0 to 15mph. You then spent 3 seconds in 2nd gear and went from 15mph to 30mph. Your instantaneous acceleration in 1st gear is 7.5 mph/s. In 2nd gear, it was 5mph/s [(30-15)/3]. Your average acceleration is 30/5 = 6mph/s. This is the equivalent acceleration you would have needed to maintain to go from 0 to 30mph in 5 seconds.

This is what we did in our labs we calculated instantaneous acceleration

Ave. Velocity and Acceleration

Simpler to calculate

Average Velocity=The change in displacement/time

Example- Traveled a total distance of 440 miles north. Trip took 8 hours. What was the average velocity? 55 miles/hr North

Average Acceleration= The change in velocity(final-initial)/time

Example- sprinter on 100 m race (14m/s-0 m/s)/ 9s =1.56m/s/s