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**Balanced & Unbalanced Forces**

D. Crowley, 2007

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**Balanced & Unbalanced Forces**

Friday, April 21, 2017 Balanced & Unbalanced Forces To be able to represent forces using arrows, and to understand the affects of balanced and unbalanced forces

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Word search Using the word search, see if you can identify the key words Stick your word search into your book! You have just five minutes, good luck!

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**Balanced forces - stationary / steady speed**

Push & Pull Forces Remember, we use arrows to represent force - the bigger the force, the bigger the arrow is The arrow points the way the force is acting The arrows come in pairs, and if the force is balanced (not accelerating) the arrows will be the same size. If the force is unbalanced (accelerating) the arrows will be different lengths… Balanced forces - stationary / steady speed Unbalanced forces - acceleration

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**Car moving at a steady speed**

Demonstration Remember a balanced force means there is no change in acceleration - so if an object is stationary, it will remain still, and if it was already moving, it will stay at that constant speed An unbalanced force means there is a change in acceleration, in the direction of the greater force Car stationary (balanced force) Car moving at a steady speed (balanced force) Car accelerating (unbalanced force)

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Push & Pull Forces Have a go at the worksheet - try and identify where the forces are, and represent them with an arrow - think about the arrows direction (up / down / pointing left / pointing right) and the arrows size Spring (Elastic Force) (pulling up) Weight (Gravity) (pushing down)

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Push & Pull Forces What forces are involved?

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Push & Pull Forces What forces are involved?

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**Balanced? What will happen if the cyclist pedals harder?**

If the cyclist pedals harder there will be an unbalanced force, and he will begin to accelerate in the direction he is cycling

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**Balanced? What will happen one team pulls harder than the other?**

How would you know if the teams were pulling with an equal force? If the two sides were pulling with an equal (balanced) force, then there would no be a change in their velocity (i.e. both teams would stay where they are)

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Extra Questions Most pictures have more than one force affecting them (i.e gravity, reaction + push / pull forces) If the forces are the same (balanced) the object will stay still or remain at its original speed. If the forces are different (unbalanced) then the object will accelerate in that direction In picture (b) - with the lady is pushing the shopping trolley with more force (4N), whilst the resistance is less (2N). This means the trolley is accelerating in the direction the lady is pushing The length of the arrow is longer, because there is an unbalanced force Friction is a force which slows objects down, e.g. drag, air resistance, the force used in brakes to stop objects

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**Push & Pull Forces What forces are involved? Reaction Reaction**

Contact (pull) Contact (pull) Contact (pull) Friction Contact (pull) Contact (push) Elastic Elastic Gravity Gravity Gravity Reaction Reaction Reaction Friction Reaction Contact (push) + Gravity Contact (pull) Contact (pull) Contact (pull) Friction Reaction + Friction Gravity Gravity Gravity Gravity Contact (push) + Gravity

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**Push & Pull Forces What forces are involved? Reaction Elastic**

Contact (pull) Reaction Gravity Reaction Reaction Contact (push) Contact (push) Friction Friction Gravity Gravity Gravity

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