Topic 1/2 - Motion & Forces

What is a scalar?

A quantity with magnitude/size only - no specific direction.

What is a vector?

A quantity with magnitude/size and direction.

What is a scalar?

A quantity with magnitude/size only - no specific direction.

What is a vector?

A quantity with magnitude/size and direction.

Give examples of scalar quantities

• Speed

• Distance

• Mass

• Energy

• Temperature

Give examples of vector quantities

• Velocity

• Displacement

• Weight

• Force

• Acceleration

• Momentum

Is speed a vector or scalar?

Scalar

Is velocity a vector or scalar?

Vector

Is distance a vector or scalar?

Scalar

Is displacement a vector or scalar?

Vector

Is mass a vector or scalar?

Scalar

Is weight a vector or scalar?

Vector

Is energy a vector or scalar?

Scalar

Is momentum a vector or scalar?

Vector

Is temperature a vector or scalar?

Scalar

Is force a vector or scalar?

Vector

Is acceleration a vector or scalar?

Vector

Define: Distance

How far apart 2 objects are.

Define: Displacement

How far apart 2 objects are in a straight line.

Define: Speed

How quickly an object travels in a given time.

Define: Velocity

How quickly an objects travels in a particular direction.

Define: Instantaneous speed

Speed at a particular point in time.

Define: Acceleration

Change in velocity within a given time.

What is uniform acceleration?

Constant acceleration

Which 3 calculations link speed, distance and time?

Speed = Distance / Time

Distance = Speed x Time

Time = Distance / Speed

Calculate: Speed

Speed = Distance / Time

Calculate: Distance

Distance = Speed x Time

State the symbols for speed, distance and time.

Speed = s

Distance = x

Time = t

State the units for speed, distance and time.

Speed = m/s

Distance = metres

Time = seconds

Which 3 calculations can we use for acceleration?

1. Final - Initial / Time

2. (final velocity)² – (initial velocity)² = 2 × acceleration × distance

3. Resultant Force = Mass x Acceleration

State the units for acceleration, velocity, time and distance.

Acceleration = m/s²

Velocity = m/s

Time = seconds

Distance = metres

State the symbols for acceleration, velocity, time and distance

Acceleration = a

Velocity = v

Time = t

Distance = x

State the symbols for final and initial velocity

Final - v

Initial - u

How can you find the speed from a distance / time graph?

Change in vertical / change in horizontal.

On a distance / time graph, what does the gradient of the line show?

Speed/Velocity

On a distance / time graph, what does the flat line show?

Object has stopped/is stationary

Describe what is happening at A, B, C and D

• A - Increasing speed; it’s accelerating

• B - Constant speed

• C - Decreasing speed; decelerating

• D - Stationary

On a velocity / time graph, what does the gradient of the line show?

Acceleration

On a velocity / time graph, how do you calculate acceleration?

Change in velocity / change in time

On a velocity / time graph, what does a steeper line mean?

Greater acceleration

On a velocity / time graph, how do you calculate distance?

Area under graph

Describe what is happening at A, B, C and D

• A - Constant acceleration + Increasing velocity

• B - Constant velocity

• C - Constant deceleration + Decreasing velocity

Define: Mass

The quantity of matter in an object.

Define: Weight

The force an object exerts due to gravity.

Is mass the same everywhere?

Yes; it never changes.

Is weight the same everywhere?

No; it changes depending on gravity.

Calculate: Mass

Weight / Gravitational field strength

Calculate: Weight

Mass x Gravitational field strength

Which 3 calculations link mass, weight and gravitational field strength?

Weight = mass x gravitational strength

Mass = Weight / Gravitational strength

Gravitational strength = Weight / Mass

State the units for weight, mass and gravitational field strength

Weight = N

Mass = Kg

Gravitational field strength = N/kg

State the symbol for weight, mass and gravitational field strength

Weight = w

Mass = m

Gravitational field strength = g

What is the typical walking speed?

1.5 m/s

What is the typical running speed?

3 m/s

What is the typical cycling speed?

5.5 - 6 m/s

What is the typical car speed?

13 - 30 m/s

What is the typical aeroplane speed?

250 m/s

What is the typical train speed?

50 - 55 m/s

What is a force?

A push, pull or twist.

How does a force being exerted change an object?

Changes an objects speed, direction or shape.

Complete: Forces always appear in ___

Pairs

Name the 2 force pairs

Action and reaction force.

What is the resultant force?

Single overall force used to represent ALL the forces acting on an object.

Which type of diagram can be used to represent the forces acting on an object?

Free body diagram

What does the length of an arrow in a free body diagram show?

Magnitude/Size of the force.

What does the direction of an arrow in a free body diagram show?

Direction of force.

If the backwards force is greater than the forwards force, what is happening to the object?

Objects is decelerating.

If the forwards force is greater than the backwards force, what is happening to the object?

Object is accelerating.

If the forcing acting on an object are equal/balanced, what is happening to the object?

Object is stationary or moving at a constant speed/velocity.

If the force is acting in the opposite direction of the force, what happens to the object?

Object will decelerate.

If the force is acting in the same direction of the force, what happens to the object?

Object will accelerate.

When forces occur, what is transferred?

Energy

What happens when all the forces on an object balance out?

Equilibrium

Define: Contact forces

Forces that occur when 2 objects are are in direct physical contact with eachother.

What is a force called when it occurs between objects physically touching?

Contact force

Define: Non contact forces

Forces that occur when objects are not physically touching.

What is a force called when it occurs between objects not physically touching?

Non contact forces

Give examples of contact forces

• Reaction force

• Tension

• Friction

• Air resistance

• Upthrust

Give examples of non contact forces

• Magnetism

• Gravity

• Electrostatic force

Which force is acts on objects at rest on a surface?

Reaction force

Which force is acts on objects being stretched?

Tension

Which force is acts on two objects sliding past each other?

Friction

Which force is acts on objects flying through the air?

Air resistance

Which force is acts on objects partially or completely submerged in water?

Upthrust

Which force causes objects to move?

Thrust

Which force is acts on any magnetic material in a magnetic field?

Magnetism

Which force is acts on any charged particle in an electric field?

Electrostatic force

Which force is acts on any mass in a gravitational field?

Gravity

Are forces balanced when the resultant force is equal to or more than 0N?

Equal to 0 Newtons.

Are forces unbalanced when the resultant force is equal to or more than 0N?

More than 0 Newtons.

When resultant force is equal to 0 Newtons, are forced balanced or unbalanced?

Balanced

When resultant force is more than 0 Newtons, are forced balanced or unbalanced?

Unbalanced

What is the resultant force if all forces are balanced?

0 Newtons.

What is Newton’s 1st law?

A resultant force is required to change the motion of an object. If there is no resultant force acting on an object and forces are balanced, motion will remain constant.

If an object is already at rest, the object will remain stationary. If the object is already moving, it will continue to move in the same direction at the same speed.

Which of Newton’s Laws states that a resultant force is required to change the motion of an object?

Newton’s 1st Law.

What happens to an object if all the forces are balanced?

• If the object is already stationary, then it will remain stationary

• If the object is already moving, it will continue to move in the same direct at the same speed

What is Newton’s 2nd law?

Non zero resultant forces acting on an object cause the object to accelerate. Acceleration depends on:

• Size of the force

• Mass of the object

Which of Newton’s Laws states that a non zero resultant force acting on an object cause the object to accelerate; acceleration depends on size of the force and mass of the object?

Newton’ 2nd Law.

What does the acceleration of an object depend on?

Size of force + Mass of object

What equation is linked to Newton’s 2nd law?

Force = Mass x Acceleration

Calculate: Resultant Force

Mass x Acceleration

Which 3 equation links resultant force, mass and acceleration?

Force = Mass x Acceleration

Mass = Force / Acceleration

Acceleration = Force / Mass

State the symbols for resultant force, acceleration and mass

Resultant force = f

Mass = m

Acceleration = a