Physics- Forces Flashcards by Solah Hayat

What is the equation for Speed?
Rearrange this
What are their units?

Speed = Distance / Time
Distance = Speed x Time
Time = Distance / Speed
SPEED - Metres per second (m/s)
DISTANCE - Meters (m)
TIME - Seconds (s)

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What is a Scalar quantity?
Give some examples

A Scalar quantity only has MAGNITUDE (size)
eg- distance, speed, time, mass, energy

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What is a Vector quantity?
Give some examples

A Vector quantity has both MAGNITUDE and DIRECTION
eg- displacement, velocity, acceleration , force

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What are speed and velocity used to measure?

Speed and Velocity can both be used to measure how quickly something is moving, in metres per second.

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What is the difference between Distance and Displacement?

Distance and Displacement are both measured in metres, but show how far something has travelled in different ways.
DISTANCE shows how far an object has travelled
DISPLACEMENT shows how far an object is relative to it’s starting position, (to do with direction). So how far it is from where it started.

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What does a negative displacement mean?

Negative Displacement- finished behind the starting line.

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What does a negative velocity mean?

A negative velocity means it is travelling in the reverse direction.

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What is the equation for Velocity?
Rearrange this

Velocity = Displacement / Time
Displacement = Velocity x Time
Time = Displacement / Velocity

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What are Distance- Time Graphs used for?

Distance - Time graphs can be used for calculating the speed of a moving object by calculating it’s gradient.

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Distance Time Graphs:
The Steeper the line…
Lines that aren’t straight represent…
A straight horizontal line means…
A line below the horizontal axis represents…

The greater the speed
a speed that is changing, so straight lines mean constant speed
No movement, stationary
an object with a negative displacement

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How do you find the gradient on a graph?

Pick two points on a line, a good distance apart, and do Change in y / Change in X

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What is acceleration?

Acceleration is the rate at which the speed of a moving object is changing.

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What is the equation for Acceleration?
Be able to rearrange this
What is the unit for Acceleration?
What is the equation for final speed?
What is the equation for time?
How would you find the initial speed on a speed- time graph?

ACCELERATION = CHANGE IN SPEED / TIME
a = (v-u) / t
v= final speed
u= initial speed
The unit for Acceleration is m/s squared
Final Speed = Initial Speed + Acceleration x Time
OR v = u + at
Time = (Final speed - Initial speed) / acceleration
Where the time is at 0, on the y intercept.

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A negative value for acceleration means…

the object is slowing down (deceleration or retardation)

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What two things can a Speed- time graph used for and how?

A Speed - time graph can be used for calculating the acceleration of a moving object, simply by calculating it’s gradient.
It can also be used for calculating the DISTANCE TRAVELLED by a moving object, simply by calculating the area under the graph.
This can be done by:
-Counting squares
-Finding the area under the triangle (1/2 bh)
-Finding the area under the rectangle (bh)
-Finding the area under the trapezium -1/2(a+b)h
-Or a combination of the above

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Speed - Time Graphs:
The steeper the line…
A negative Gradient means..
A level line means…
A level line following the horizontal axis means..

the greater the acceleration
the object is decelerating
The object is travelling at a constant speed
The object is stationary/ not moving

A force is a…

push or a pull

Forces cause objects to change…
They may also…
Forces can work through object being…

-Change Speed (Start, Speed up slow down or stop).
-Squash or Stretch an Object
-In contact with each other or sometimes at a distance

What is the unit for force?

The unit for force is the Newton (N).

Name the 6 different forces?

-Weight
-Reaction
-Upthrust or Lift
-Friction or Air Resistance
-Thrust or Driving force
-Tension

Describe Weight:

The effect of Gravity on a mass, acting straight down.

Describe Reaction:

The effect of a surface pushing on an object, at right angles to the surface.

Describe Upthrust or Lift:

The supporting force exerted by a fluid on an object, acting upwards.

Describe Friction or Air resistance:

A resistive force attempting to slow an object, (due to rubbing on a surface, or against the air), opposing the motion.

Describe Thrust or Driving Force:

The pull of a machine, doing work to move an object, in direction of motion.

Describe Tension:

The pull of a rope, chain or wire, acting along the rope away from the object.

What is the Resultant force?

The Resultant force is a measure of how unbalanced the forces are, and should also have it's direction stated. It's basically the overall force acting on an object when multiple forces are applied.

What if the forces acting on an object are balanced?

If the forces acting on an object are balanced, the Resultant force is zero, and so the object moves at a constant speed.

Describe the state of the forces of an object, if the object is not moving.

If the object is stationary, there must be no driving force present and the forces acting on the object are balanced.

If the forces acting on an object are unbalanced...

there is a resultant force and so the object's speed will change.

The object will accelerate in the direction of...

the resultant force.

A resultant force acting backwards... (the direction of the DRIVING FORCE always determines...

decelerates the object the direction of motion)

What is the difference between Mass and Weight?

Mass is a measure of how much matter makes up an object, measured in kilograms, while Weight is the force exerted by an object, caused by the pull of gravity, measured in newtons. Also, the mass of an object will NOT change in different parts of the universe but the weight WILL bc the greater the Gravitational Field Strength, the greater the Weight.

What is the equation for Weight? Make sure you are able to rearrange this equation.

Weight = Mass x Gravitational Field Strength.

Another expression that is similar to 'Gravitational Field Strength' is....

'acceleration due to gravity'. The numbers are the same but the unit is m/s squared instead of Newtons.

What is Newtons First law?

An object will remain at rest unless acted on by an external and unbalanced force. An object will remain in motion unless acted on by an external and unbalanced force.

What is Newtons Second law?

The rate of change of momentum of a body is proportional to the resultant force acting on the body and is in the same direction.

What is the equation for Force?

FORCE = MASS x ACCELERATION

What is Newtons Third Law?

For every action (force) in nature, there is an equal and opposite reaction. So if object A exerts a force on object B , object B also exerts an equal and opposite force on object A. In other words, forces result from interactions.