Forces and Their Effects

Physics Checkpoint @ferrytanoto

You cannot see a force but you

can see what it does. You can also feel the

effect of a force on your body.

A force is

a push or a pull

What can a force do?

A force can

make an object move.

A force can make

a moving object stop.

A force can

change the speed of a moving object.

A force can accelerate an object. The larger the force on the object, the greater the acceleration if the mass stays constant. The larger the mass of the object, the smaller

the acceleration if the force stays constant.

Newton’s Second Law of Motion:

Force (N) = mass (kg) x acceleration (m/s2)

A force can

change the direction

of a moving object.

A force can

change the shape

of an object.

How to measure a force?

A force can be measured with

a Newton spring balance.

The SI unit for measuring force is

the Newton (symbol N).

There are two main types of forces:

contact forces and

non-contact forces.

A contact force occurs when the object or material

exerting the force touches the object or material on which the

force acts.

A non-contact force occurs when the objects or

materials do not touch each other.

Contact Forces• Impact force

When a moving object collides with a stationary object an impact force is exerted by one object on the other.

• Strain forceWhen some materials are squashed, stretched, twisted or bent they exert a force which act in the opposite direction to the force acting on them. These materials are called elastic materials and the force they exert when they are deformed is called a strain force.

Impact force

When a moving object collides with

a stationary object an impact force is exerted by one object on the other.

Strain force

When some materials are squashed, stretched, twisted or bent they exert a force which act in the opposite direction to the force acting on them. These materials are called elastic

materials and the force they exert when they are deformed is called a strain force. When the force applied to the material is removed the strain force exerted by the

material restore the deformed material to its original shape.

Tension

Tension is a strain force that is exerted by a

stretched spring, rope or string. At each end

the tension force acts in the opposite direction to the pulling force.

Non-contact ForcesThey all exert their force without having to

touch the object

• Magnetic forces

• Electrostatic forces

• Gravitational forces

Magnetic Force

A magnet has a north-seeking pole and a south-seeking pole, known as north pole

and south pole. If you pick up two magnets and bring them together, you will feel a force either pushing or pulling each

other. The same poles attract each other

while different poles repel each other.

Magnetic Force

A magnet can also exert a non-contact force on

objects made of iron, steel, cobalt or nickel. Either pole of the magnet exerts a pulling force on these magnetic materials.

The strength of the force increases as the magnet and the magnetic material are

brought closer together.

Maglev (Magnetic Levitation) Train

Maglev (Magnetic Levitation) Train

Electrostatic Force

If certain electrical insulator materials are rubbed an electrostatic charges (positive

charge and negative charge) develop on them.

Similar charges repel each other while opposite charges attract each

other.

Gravitational Force

The force that exists between any two masses because

of their mass is called the gravitational force.

•F is the force between the masses,

•G is the gravitational constant (which is approximately equal to 6.674×10−11 N m2

kg−2)

•m1 is the first mass,•m2 is the second mass, and•r is the distance between the masses.

Gravitational Force

The gravitational force between the Sun and all the planets in the Solar System holds the

planets in their orbits

The gravitational force between an object on the Earth and the Earth itself pulls the object down towards the centre of the Earth and is

called the weight of the object.

Robert Hooke

The extension of a spring is proportional to the mass attached to it.

F = kxF = applied force (N), x = extension (m),

k = force constant for object under test (N/m)

However, the addition of mass to a spring beyond a limit, called the elastic limit, it no longer extends

proportionally to the mass anymore. It is permanently deformed.

The spring beyond its elastic limit was in a state known as plastic deformation.

A Spring Balance

This instrument uses Robert Hooke’s discovery. The scale

on the balance is calibrated in

newton so it is sometimes

called a Newton Spring Balance or a

newtonmeter.

5 N

5 N