Forces between objects Flashcards

1
Q

What is a force?

A

A force is a push or pull that is caused by interacting with something.

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2
Q

What are the two types of force?

A

All forces are either contact or non-contact forces.

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3
Q

When is a force a contact force?

A

When two objects have to be touching for a force to act, the force is called a contact force.

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4
Q

Examples of contact forces

A

Friction, air resistance, tension in ropes, normal contact force, etc.

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5
Q

When is a force a non-contact force?

A

If the objects do not need to be touching for the force to act, the force is a non-contact force.

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6
Q

Examples of non-contact force

A

Magnetic force, gravitational force, electrostatic force, etc.

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7
Q

What does Newton’s third law of motion state?

A

Newton’s third law of motion states that when two objects interact with each other, they exert equal + opposite forces on each other.

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8
Q

What is the unit of force?

A

The unit of force is the newton abbrieviates as n.

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9
Q

Examples of Newton’s third law of motion

A

→ A boxer who punches a bag with a force of 100N experiences an equal + opposite force of 100N from the bag.
→ The weight of an object is the force of gravity on an object due to the Earth. The object exert equal + opposite forces on the Earth.
→ Two-roller skaters pull on opposite end of a rope. The skaters move towards each other because they pull on each other with equal + opposite forces(Two newton-metres could be used to show this).
→ The Sun + Earth are attracted to each other by the gravitational force. This is a non-contact force. An equal but opposite force of attraction is felt by both the Sun and the Earth.

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10
Q

How to get a car stuck in mud out of the mud?

A
  • A car stuck in mud can be difficult to move.
  • A tractor can be useful here.
  • At any stage, the force of the rope on the car is equal to the force of the car on the rope.
  • To pull the car out of the mud, the force of the mud on the tractor need to be greater than the force of the mud on the car.
  • These two forces are not equal + opposite to each other.
  • The ‘equal and opposite force’ to the force of the mud on the tractor is the force of the tractor on the mud.
  • The ‘equal an opposite force’ to the force of the mud on the car is the force of the car on the mud.
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11
Q

What is the driving force?

A

The driving force on a car is the force that makes it move.

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12
Q

What else can the driving force be know as?

A

This is sometimes called the engine force or the motive force.

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13
Q

What does the driving force do?

A
  • The force pushes the car forward because there is no friction between the ground and the tyre of each drive wheel.
  • Friction acts where the tyre is in contact with the ground.
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14
Q

What happens when the car moves forward?

A

When the car moves forward:
* The force of the friction of the road on the tyre is in the forward direction.
* The force of the friction of the tyre on the road is in the reverse direction.
→ The two forces are equal + opposite to each other.

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