Chapter (1) Forces and Motion

What is mass measured in?

kilograms (kg)

What is distance measured in?

meters (m)

What is speed measured in?

meters per second (m/s)

What is acceleration measured in?

Meters per second squared (m/s²)

What is weight measured in?

Newtons (N)

What is the equation for velocity? SUVAT

v = u + at (velocity = initial velocity + (acceleration x time)

What do the letters in SUVAT stand for?

S- Displacement, U - Initial velocity, V - Final velocity, A - Acceleration, T - Time

What is the equation for velocity?

v=d/t

What is the equation for velocity² Squared? SUVAT

v² = u² + 2as

What's the equation for average speed?

average speed = distance moved/ time taken

What's the equation for force?

force = mass x acceleration, F=ma

What's the equation for weight?

Weight = mass x gravitational field strength, w=mg

What's gravitational field strength on earth?

10 N/Kg

What's the equation for momentum?

momentum = mass x velocity (p=mv)

What's the equation for force (including momentum)?

force = change in momentum/ time taken

What's the equation for a moment?

moment = force x perpendicular distance from pivot

Define velocity.

a speed in a defined direction

Define acceleration.

When an object's speed is either increasing or decreasing

Define force.

A push or a pull

What is the equation for stopping distance?

Stopping distance = thinking distance + braking distance

What is the equation for thinking distance?

thinking distance = speed x reaction time

What does the gradient of a distance-time graph represent?

speed.

What does a flat gradient on a D-T graph mean?

the object has stopped.

What does a steep gradient on a D-T graph mean?

the object is going fast

What does a steepening curve mean on a D-T graph?

object is accelerating

What does a levelling curve mean on a D-T graph?

object is decelerating

How do you find speed at a point on a D-T graph which is a curve?

Take the tangent at a point and calculate speed.

How would you investigate motion with a toy car?

1. Mark line on ramp

2. Measure distance between each light gate

3. Let go of car so it rolls down ramp

4. Light gate should log time car passes through

5. repeat the experiment several times and get avg. time

6. Use times and distances between light gates to calculate avg. sped.

What equipment would you need to investigate motion with a toy car?

Toy car, Light gate, Ramp, runway and machine with data-logging software.

In investigation of motion with a toy car, why mark a line on ramp?

To ensure car starts at the same point each time.

How do light gates work?

When the car passes throught the gate, a beam of light is broken and the time is recorded by data-logging software.

Why are light gates more accurate?

There are no timing errors as a result of a person reacting slowly.

What can you use instead of a light gate?

Stopwatch with lap function.

What are the independent variables of toy car experiment?

1. Mass of car

2. Material of ramp

3. Acceleration

4. Angle of Ramp

5. Type of car

How does mass of car affect toy car experiment?

Loading weights onto the car will affect average speed (make sure wheel axles don't grind)

How does material of ramp affect toy car experiment?

There will be different levels of friction with different materials, make sure material is laid flat so it doesn't change angle of ramp.

How do you make acceleration affect toy car experiment?

Gravity, start the car higher up.

How does angle of ramp affect toy car experiment?

changing the angle of the ramp changes speed.

How does type of car affect toy car experiment?

different cars have different sizes, shapes and weights.

Essentially what is acceleration?

Change in velocity.

What are the units for acceleration?

m/s²

What does the gradient show on a V-T graph?

acceleration

What does it mean when the gradient is 0 on a V-T graph?

The speed is steady and the object isn't accelerating.

On a V-T graph, what does a steep gradient mean?

A steep gradient means greater acceleration/ deceleration.

What do positive and negative gradients mean on V-T graphs?

Positive: Acceleration, Negative: Deceleration.

What does a curve mean on a V-T graph?

changing acceleration.

What does a curve ( ╯) mean on a V-T graph?

Increasing acceleration.

What does a curve (╭) mean on a V-T graph?

Decreasing deceleration.

What does a curve (╮) mean on a V-T graph?

Decreasing deceleration.

What does a curve (╰) mean on a V-T graph?

Increasing deceleration.

How do you find distance on a V-T graph?

By finding the area underneath or distance = velocity x time.

What happens when you push or pull something?

You exert a force.

What can an exerted force do?

- Change the shape of an object (stretch/ squash/bend/break)

- Change the speed of an object (throwing/catching)

- Change the direction in which something's travelling (a steering wheel for car)

What is a contact force?

When two objects have to be touching for a force to act (i.e your hand touches something).

What are non-contact forces?

Forces that act over a large distance without the need for two objects to be touching.

Give 3 examples of non-contact forces

gravitational, electrostatic, magnetic.

Give 5 examples of contact forces

friction, air resistance, normal contact force, upthrust (buoyancy), tension.

Give real life examples for non-contact forces.

1. When a person jumps, they'll land back on the ground because of gravity.

2. The earth's in orbit around the sun because of gravity.

3. With two magnets, North and South attract.

What are vectors?

quantities that have magnitude and direction.

What are scalars?

Quantities that only have a magnitude.

What is magnitude?

size

List the vectors x10.

Displacement, Velocity, Acceleration, Area, Momentum, Moment, Gravitational Field Strength, Magnetic Field Strength, Force

List the scalars x11

Distance, speed, mass, time, volume, energy, density, pressure, temperature, voltage, power, frequency, charge

How can vectors be added?

With taking account of positive and negative and also direction.

Define friction.

Contact force that slows down moving things, it can also prevent stationary things from starting to move when other forces act on them.

Define tension.

Force which acts through a stretched rope (like two people pulling a rope).

Define weight.

The name given to the pull of gravity on an object.

What is the gravitational field strength on Earth?

10N/kg

How does gravity work?

Gravity attracts all masses but is only noticed when mass is huge like a planet. it keeps planets, moons and satellites in their orbit.

How does gravity work on the surface of a planet?

It makes things accelerate towards the ground and gives everything a weight.

How does orbit work?

Balance between the forward motion of the object and the force of gravity pulling it in.

Define Mass.

The amount of matter in an object.

Does mass ever change?

No, mass will always have the same value.

What is mass a measurement of?

How difficult it is to accelerate an object.

How is mass measured?

Using a mass balance and in kg.

What is the weight of an object?

the force of gravity pulling it towards the centre of the Earth.

Why is a 1kg mass weighing less on the mokn?

The force of gravity pulling it towards the moon is less than on the Earth.

How is weight measured?

With a spring balance or newton metre, and in Newtons,

When does gravity/weight act?

Close to a planet, it acts straight down.

Which direction is reaction force?

Perpendicular to a surface and away from it. (If a horizontal surface, force goes straight up)

When does electrostatic force occur?

Between two charged objects, direction depends on charge. (attract/repel)

What is thrust?

Push or Pull due to an engine or rocket speeding something up.

What does drag, air resistance and friction do?

Slow something down.

When does lift occur?

On an aeroplane wing.

When does tension occur?

In a rope or cable.

What two forces balance each other out on a car? (vertical)

Reaction and weight.

What does every object with a weight have?

A reaction force back from the surface it's on, if not it'd just keep falling.

What would happen if an object moves through a fluid?

It feels drag in the opposite direction to its motion.

What is a fluid?

Air or water

There is a person standing on the ground, why isn't she falling through?

The girl's weight/ gravity pulls the girl downwards towards the Earth. The Earth exerts a force of the same kind back on the girl. The Normal force is the weight of the girl on the Earth, and the reaction is the Earth on the girl.

If an object has no force propelling it along, why does it stop?

Providing it's not in a vacuum, an object will always slow down and stop because of friction.

How do things travel at a steady speed?

There must be a force to counteract the friction.

What are the 3 ways in which friction can occur?

1. Solid surfaces which are gripping

2. Solid surfaces sliding past each other

3. Resistance or drag from fluids

How can friction between solid surfaces be reduced?

By putting a lubricant between the surfaces.

Give examples of a lubricant.

Oil and Grease

What effect does friction between surfaces have?

It can cause the wear of the two surfaces in contact.

How can you reduce resistance from fluids?

Keep the objects streamlined.

Give an example of a feature which reduces speed and increases friction.

Roof boxes on cars destroy their streamlined shape and slow them down.

Parachutes have a huge surface area to increase drag

Give an example of a feature used to reduce friction and increase speed.

Lorries and caravans have deflectors on them to make them more streamlined and reduce drag.

What is stopping distance?

Stopping distance = thinking distance + braking distance