Mechanics of Forces: Classification, Levers, Inclined Planes, Pulleys, and Wheels, Slides of Physics

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Forces Introduction

• Intersections

• smart car crash

• stopping distance

• Crash investigation

Levers

• You can use a

mechanism to move

something more easily.

• Force Multiplier

• force you produce is

bigger than the force

you apply

• Mechanical Advantage

• 3 types

= Effort

Load =

Class 2

• The fulcrum is at one

end.

• You apply force at the

other end and the force

you produce is in the

middle.

Class 3

• apply the force in the

middle and the force

you produce is at the

opposite end.

• They reduce the force

you apply, giving you

much greater control.

Pulleys

• Two or more wheels and a loop of rope

around them creates a lifting machine.

• Each time the rope wraps around the wheels,

you create more lifting power or mechanical

advantage.

Pulleys

• Pulleys transfer rotation

from one shaft to

another.

• Same diameter = same

speed rotation.

• Large drive pulley

makes a smaller pulley

rotate faster.

• If the belt is crossed

rotation is in the

opposite direction.

FORCES

Forces are pushes or pulls (a combination is a twist ).

Objects are stationary when forces are balanced

gravity is always acting but we don’t keep falling due to a support force

Forces can be measured using a Newton meter.

BALANCED FORCES An unbalanced forces cause changes to objects motion (speed or direction), or shape.

If a force acts on a stationary object and causes motion, the object has gained kinetic (movement) energy. Friction will stop the object moving.

Types of force: Gravity

Electrostatic

Magnetism Tension – the force in rope, etc

Friction – the force that opposes motion

Support Bouyancy – in the water

Lift – in the air (planes/birds)

FORCE PAIRS

Forces act in pairs (e.g. thrust and friction, gravity and support).

Force diagrams show the forces acting on an object and whether they are balanced or unbalanced.

A rrow size represents force size if no measurements are available.

Force pairs

• What are the

missing terms?

• Buoyancy

• Drag

• Thrust

• Weight

FORCE AND MOTION What happens when you apply (using a Newton meter) a small constant force to a trolley and time it over a set distance?

Small constant force

An unbalanced force causes acceleration.

The trolley should accelerate because…

Set distance

FORCE AND MOTION What happens when you apply (using a Newton meter) a small constant force to a trolley carrying a 1kg mass and time it over a set distance?

Small constant force

The larger the mass the slower the acceleration

The trolley should accelerate but slower than previously because…

Set distance

1Kg

WEIGHT FORCE

Weight is a force. It is therefore measured in… An object’s weight depends on two things…

Newtons (N)

Gravity

• varies depending where you are
• 10ms -2^ or 10N/Kg on Earth Mass
• does not vary
• measured in Kg
• A man with mass of 75Kg on earth weighs 750N BUT on the moon he weighs 125N Docsity.com

MASS AND WEIGHT

1. a. What is mass? b. What is it’s unit?
2. a. What is Weight? b. What is it’s unit?
3. ON EARTH: 1N = kg 1kg = N
4. How would your mass and weight change if you went to Jupiter?