GSCE Forces

COMPLETED Cognito Notes

What is a force?

A push or pull that acts upon an object as a result of that object’s interactions with its surroundings

What is force measured?

Newtons

Is force vector or scalar?

Vector

Why is Force a vector quantity?

It has both magnitude and direction

What is contact force?

When objects are physically touching

What is non-contact force?

When objects aren’t physically touching

What are contact forces?

Tension, Friction and Reaction Force

What are non-contact forces?

Electrostatic, Magnetic and Gravatitional Forces

What happens when non-contact force move away from objects?

Decrease as the object gets further apart

What is normal contact force?

Two objects exerting equal and opposite forces

Why is air resistance a contact force?

There is physical contact between an object and the particles in the air.

What are scalar quantities?

They have magnitude only.

What are vector quantities?

They have magnitude and direction.

What are examples of scalar quantites?

Speed, Temperature, Mass and Distance

What are examples of vector quantities?

Velocity, Displacement, Acceleration, Force and Momentum

What are Free body Diagrams?

They use arrows to show all of the forces acting on an object.

What does the length of the arrow indicate?

The magnitude.

What does the direction of the arrow indicate?

The direction.

What is the resultant force?

The overall of force on an object.

What happens when forces are balanced?

The object is in equilibrium.

What is deformation?

A change in the shape of an object as a result of forces being applied to it.

What is Elastic Deformation?

When an object does return to its original shape after the forces have been removed.

What is Inelastic Deformation?

When an object does not return to its original shape after the forces have been removed.

What is extension?

The increase in length of a spring when its stretched or decrease in length when the spring is compressed.

What is spring constant?

How many newtons of force it would require to stretch the object by 1 metre.

What unit is spring constant?

N/m

What makes object stiff?

It has a higher spring constant

What is Hooke’s Law?

F=Ke

What is the elastic limit?

The point at which an object being stretched starts deforms, when Hooke’s Laws stop.

What is a moment?

A moment is the rotational or turning effect of a force.

What is the equation for moments?

M=fd

Why is a seesaw balanced?

The total clockwise moment is equal to the total anti-clockwise moment.

How do levers work?

They transmit the turning effect of a force by using the principle of moments.

How do gears move?

They turn in opposite directions.

The ratio of the turning effect of the two gears is proportional to the ratio of the radius of the two gears.

What exerts pressure?

Gases, solid and fluids.

What are fluids?

Gases or liquids.

How do fluid exerts pressure

Particles collide with the container exerting a force-pressure

What is the equation for pressure?

P=F/A

What factors determine pressure exerted by a liquid?

Depth, Density and Gravitational Field Strength

How does Depth affect pressure?

The more depth, the more pressure is exerted

How does density affect pressure?

More dense liquids exert greater pressure.

What is Gravitational Field Strength?

9\.8 N/m

What is the formula for pressure in a liquid?

P=hpg

What is upthrust?

The pressure on the bottom of the object being greater than the prssure on the top of the object.

What happens to objects denser than the liquid?

They will sink.

What is Atmospheric Pressure?

The total force of all the air particles constantly colliding with everything.

Why is atmospheric pressure greater underwater?

More gas particles to collide with object and air is more dense.

What is the equation for velocity?

V=s/t

What is acceleration?

The rate of change in velocity.

What is the formula for acceleration?

a= change in v / t

What another the formula for acceleration?

2as= v squared-u squared

What is the y-axis on a distance/time graph?

Distance

What is the x-axis on a distance/time graph?

Time

What is a flat line mean on a distance/time graph?

Stationary Object.

What is the x-axis on a velocity/time graph?

Time

What is the y-axis on a distance/time graph?

Velocity

What is a flat line mean on a velocity/time graph?

Constant Speed

What is the gradient of a velocity/time graph?

The acceleration or deceleration of an object.

What is terminal velocity?

When an object is falling with constant velocity.

What causes an object to fall?

Weight

What affects the size of air resistance?

Moving objects colliding with particles in air.

What is Newtons first law?

A resultant force is required to change the motion of an object.

What happens when object has no resultant force?

It will continue moving at the same velocity.

What is Newtons second law?

An object’s acceleration is directly proportional to the force applied to it, and inversely proportional to its mass.

What is Newtons Second Law Formula?

F=ma

What is Newtons Third Law?

The forces that two objects exert on each other when they interact are equal and opposite.

What is stopping distance?

The total distance a car travels from when the driver notices the obstruction to when it stops.

What is the formula for Momentum?

P=mv

What is conservation of mass?

The total momentum before a collision is equal to the total momentum after the collision.

What is a formula for change in momentum?

F= change in pressure/ time

What is a formula for change in momentum, involving velcoity?

F= final velocity- inital velocity / times

Why are safety features used in cars?

To slow the rate at which momentum is lost.

What are safety features in cars to slow loss of momentum?

Airbags and Crumple Zones

What is velocity?

Displacement over time.

What is inertia?

An object's mass is also a measure of how difficult it is to change the object's motion.

What is the centre of mass?

The point at which all mass appears to be.

When will an object topple?

When it’s centre of mass is outside it’s base.

What is the first step of Hooke’s Laws practical?

Measure the original length of the spring..

What is the second step of Hooke’s Laws practical?

Hang different masses on the spring and measure the length of the spring in each case.

What is the third step of Hooke’s Laws practical?

Adding masses to the spring increases the downwards force as each mass has weight.

What is the fourth step of Hooke’s Laws practical?

The extension of the spring equals the length with masses minus the original length

What is the fifth step of Hooke’s Laws practical?

Plot a graph with the extension of the spring on the x-axis and force on the y-axis.

What is Centre of Mass?

The single point through which the weight of the object can be said to act.

What is Inertial Mass?

Inertial Mass: A measure of how hard it is to change an object’s velocity. It is defined as the ratio of force over acceleration.