# P2.2 Newtons Laws

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How do forces arise?

Pairs of forces arise when objects interact.

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What is Newton's third law?

Newtons Third Law - "for every action there is an equal and opposite reaction" In simpler terms: forces always come in pairs

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What are non contact forces?

objects interact without touching each other electrostatics, magnetism, gravity. These arise because charges, magnets and masses interact at a distance. Electric charges and magnets both repel and attract, but gravity only attracts, results of fields

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What is a field?

A field is a region where an electrical charge, a magnetic material or a mass experiences a force.

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What is a contact force?

Solid surfaces can exert a force on objects that exert a force on them. You can draw contact force arrows from the point of contact. Examples: friction, drag, normal contact force, upthrust and tension

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What is a free body diagram?

A free body diagram is a diagram that shows the forces acting on a single object

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How do you draw a free body diagram?

Step 1: identify all non contact pairs Step 2: identify all contact pairs Step 3: focus on a single object. Draw that object with arrows showing all the forces acting on the object

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How do you identify pairs?

It is helpful to think of the pairs of forces as "the force of X on Y, and the forces of Y on X"

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Draw a free body diagram for a book on a table

Step 1: Force of the Earth on the book, and vice versa Step 2: There is the force of the table on the book (and vice versa) Step 3: Draw a diagram of just the forces on the book.

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How do you find the resultant force?

You can wokr out the resultant force or net force from your completed free body diagram. 5N to the left and 5N to the right is a resultant fore of 0. 3N to the left and 5N to the right is a resultant force of 2N to the right.

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How do you calculate resultant forces at different angles?

You can use Pythagoras theorem to calculate the resultant force. c^2 = a^2 + b^2

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What is Newtons First Law of Motion?

The motion (speed+direction) of an object does not change when the resultant force is zero

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What is resultant force?

The force when two or more forces are added together as vectors

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What is the principle of inertia?

It is the measure of how difficult it is to change an objects velocity

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What is equilibrium?

An object is in equilibrium if all the forces cancel - the resultant force is zero

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Does uniform velocity need a resultant force?

No, uniform velocity does not need a resultant force,

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What is Newtons Second Law?

If the resultant force is not zero the motion of an object (speed/direction) changes

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What can a resultant force do?

It can: change the speed of an object, change the direction of motion of an object, change both the speed and direction of motion of an object

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What is the equation for force?

Force (N) = mass (kg) x acceleration (m/s^2)

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How do you calculate acceleration?

you calculate the resultant force and then use the equation for acceleration to find the answer.

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What is the equation for acceleration?

Acceleration = force/mass

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What is terminal velocity?

The velocity that a moving object achieves when the resultant force is zero

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Give an example of terminal velocity

You accelerate (plane) your motion changes because there's a resultant force on you. The air exerts a force on you, the earth exerts a larger force. As you accelerate force of the air grows. Force of the air no longer changes, reached termin. velo.

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How do you explain the motion of objects when the forces are at an angle?

Sometimes the forces acting on an object are not all ina straightline. You can analyse this situation by resolving rhe froces so that youa re only dealing with forces that act in two directions at rgith angles

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What is momentum?

The quantity of motion of a moving body, measured as a product of its mass and velocity.

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How do you calculate momentum?

momentum (kg m/s) = mass (kg) x velocity (m/s)

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What is the law of conservation of momentum?

In any interaction or collision, the momentum before a colliion equal momentum after

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Describe an elastic collision

In an elastic collision no energy is transferred to other stores. The energy in the kinetic store stays the same.

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Describe an inelastic collision

In an inelastic collision some energy is transferred to other stores

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State the connection between the conservation of momentum and Newtons Third Law

The Logic Behind Momentum Conservation. Consider a collision between two objects - object 1 and object 2. For such a collision, the forces acting between the two objects are equal in magnitude and opposite in direction (Newton's third law).

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What is work?

The transfer of energy. Work is commonly done against gravity or friction. It can be calculated by multiplying force and distance.

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What is power?

Rate of transfer of energy

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What is the equation for work done?

Work done (J) = Force (N) x distance (m)

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What is the equation for power?

Power (W) = work done (J)/time (s)

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What is a derived unit?

Obtained by multiplication or division of the base units, and there is no introduction of numerical factors.

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## Other cards in this set

### Card 2

#### Front

What is Newton's third law?

#### Back

Newtons Third Law - "for every action there is an equal and opposite reaction" In simpler terms: forces always come in pairs

### Card 3

#### Front

What are non contact forces?

#### Back

### Card 4

#### Front

What is a field?

#### Back

### Card 5

#### Front

What is a contact force?

#### Back

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