Unit 2 - Force and Momentum

During this Unit

This unit focuses on the effects of force and momentum on motion as well as two of the fundamental forces of nature (electrical and gravity). Students will investigate how an object’s motion changes due to force. Students describe the relationship between force, mass, and acceleration and use the formula F=ma to calculate each value given different scenarios. Students only explore momentum in terms of how action and reaction forces conserve momentum. Students explore gravity and electrical forces independently of each other as naturally occurring forces that depend on the properties of the objects influenced by the forces.

 

Misconceptions:

  • Students may think an object a person is sitting or standing on does not push back with equal force, rather than all actions having equal and opposite reactions that act in force pairs.

  • Students may think friction is not a force, rather than friction being the force that brings most objects to a stop.

  • Students may think that unbalanced forces can only change an objects speed, rather than understanding that forces can change an objects direction without affecting speed.

 

Key Content Vocabulary:

  • Electrical force – a universal force between any two charged objects

  • Gravitational force – the force of attraction between all masses in the Universe

  • Law of conservation of momentum – for a collision occurring between two objects in a closed system, the total momentum of the two objects prior to the collision is equal to the total momentum of the two objects after the collision; momentum lost by first object is gained by second object

  • Law of universal gravitation – any two bodies in the Universe attract one another with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them

  • Momentum – the quantity of motion of a moving object; expressed as the product of mass times velocity

  • Unbalanced forces – forces acting on the object that are not equal in opposite directions, resulting in a change in motion

 

Related Vocabulary:

  • Action force

  • Attract

  • Balanced forces

  • Force

  • Friction

  • Gravity

  • Negative charge

  • Net force

  • Positive charge

  • Reaction force

  • Repel

  • Weight

 

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