Define Newton's first law .

An object will remain at rest or move with constant velocity unless acted on by a resultant force .

What three changes can a resultant force cause to an object's motion?

speed up slow down change direction

If the forces acting on a body are balanced , what two states could the body be in?

at rest moving at constant velocity

How is the resultant force on a body calculated from the individual forces acting on it?

The resultant force is the vector sum of all the forces acting on the body.

Since force is a vector , it is easier to split the forces acting on a body into horizontal and .......... components.

Since force is a vector , it is easier to split the forces acting on a body into horizontal and vertical components.

True or False? A car moving at a constant velocity must have zero resultant force acting on it.

True. By Newton's first law, an object moving at constant velocity is not accelerating, so the forces acting on it (such as the driving force and resistive forces) must be balanced, giving a resultant force of zero.

Define Newton's second law .

The resultant force acting on an object with a constant mass is directly proportional to its acceleration .

In what direction does the acceleration of an object act, relative to the resultant force?

The acceleration always acts in the same direction as the resultant force.

If the resultant force acting on an object opposes the direction of its motion, the acceleration is .......... .

If the resultant force acting on an object opposes the direction of its motion, the acceleration is negative .

True or False? In the absence of air resistance, a heavier object falls with a greater acceleration than a lighter object.

False. If no drag forces are present, the acceleration of a falling object is independent of its mass .

Define Newton's third law .

If Object A exerts a force on Object B , then Object B exerts a force on Object A which is equal in magnitude but opposite in direction .

What four conditions must a pair of forces meet to be a Newton's third law pair ?

same type of force same magnitude opposite in direction acting on different objects

A book rests on a table. Why are the weight of the book and the normal contact force from the table not a Newton's third law pair?

They are not the same type of force (weight and normal contact force), and both forces act on the same object (the book).

What is the Newton's third law pair to the weight of a book resting on a table?

The gravitational pull of the book on the Earth .

A useful way to describe third law pairs is: Object A pushes or pulls on Object B, and Object B pushes or pulls on .......... .

A useful way to describe third law pairs is: Object A pushes or pulls on Object B, and Object B pushes or pulls on Object A .

True or False? Two forces that are equal in magnitude and opposite in direction must always be a Newton's third law pair.

False. The forces must also be the same type of force and act on different objects . For example, the weight and normal contact force on a book resting on a table are equal and opposite but act on the same object, so they are balanced forces, not a third law pair.

A LevelPhysicsAQAFlashcardsMechanics & MaterialsNewton’s Laws of Motion

Newton’s Laws of Motion (AQA A Level Physics): Flashcards

Exam code: 7408

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FrontNewton’s First Law
Define Newton's first law.
FrontNewton’s First Law
What three changes can a resultant force cause to an object's motion?
BackNewton’s First Law
speed up
slow down
change direction
FrontNewton’s First Law
If the forces acting on a body are balanced, what two states could the body be in?
BackNewton’s First Law
at rest
moving at constant velocity

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Cards in this collection (19)

Define Newton's first law.
An object will remain at rest or move with constant velocity unless acted on by a resultant force.
What three changes can a resultant force cause to an object's motion?
- speed up
- slow down
- change direction
If the forces acting on a body are balanced, what two states could the body be in?
- at rest
- moving at constant velocity
How is the resultant force on a body calculated from the individual forces acting on it?
The resultant force is the vector sum of all the forces acting on the body.
Since force is a vector, it is easier to split the forces acting on a body into horizontal and .......... components.
Since force is a vector, it is easier to split the forces acting on a body into horizontal and vertical components.
True or False?
A car moving at a constant velocity must have zero resultant force acting on it.
True.
By Newton's first law, an object moving at constant velocity is not accelerating, so the forces acting on it (such as the driving force and resistive forces) must be balanced, giving a resultant force of zero.
Define Newton's second law.
The resultant force acting on an object with a constant mass is directly proportional to its acceleration.
State the equation for Newton's second law, including the meaning of each symbol.
$F = m a$
- F = resultant force, in newtons (N)
- m = mass, in kilograms (kg)
- a = acceleration, in metres per second squared (m s^-2)
In what direction does the acceleration of an object act, relative to the resultant force?
The acceleration always acts in the same direction as the resultant force.
How can Newton's second law be expressed in terms of momentum?
The resultant force on an object is equal to its rate of change of momentum.
$F = \frac{Δ p}{Δ t}$
If the resultant force acting on an object opposes the direction of its motion, the acceleration is ...........
If the resultant force acting on an object opposes the direction of its motion, the acceleration is negative.
True or False?
In the absence of air resistance, a heavier object falls with a greater acceleration than a lighter object.
False.
If no drag forces are present, the acceleration of a falling object is independent of its mass.
Momentum is defined as $p = m v$ . Show how this leads to the equation $F = m a$ .
$\frac{Δ p}{Δ t} = m \frac{Δ v}{Δ t}$
Since $a = \frac{Δ v}{Δ t}$ and $F = \frac{Δ p}{Δ t}$ :
$F = m a$
Define Newton's third law.
If Object A exerts a force on Object B, then Object B exerts a force on Object A which is equal in magnitude but opposite in direction.
What four conditions must a pair of forces meet to be a Newton's third law pair?
- same type of force
- same magnitude
- opposite in direction
- acting on different objects
A book rests on a table. Why are the weight of the book and the normal contact force from the table not a Newton's third law pair?
They are not the same type of force (weight and normal contact force), and both forces act on the same object (the book).
What is the Newton's third law pair to the weight of a book resting on a table?
The gravitational pull of the book on the Earth.
A useful way to describe third law pairs is: Object A pushes or pulls on Object B, and Object B pushes or pulls on ...........
A useful way to describe third law pairs is: Object A pushes or pulls on Object B, and Object B pushes or pulls on Object A.
True or False?
Two forces that are equal in magnitude and opposite in direction must always be a Newton's third law pair.
False.
The forces must also be the same type of force and act on different objects. For example, the weight and normal contact force on a book resting on a table are equal and opposite but act on the same object, so they are balanced forces, not a third law pair.

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