5.4 Battle of the forces09 January 2011

Unscramble the following words:

ntioricf

ceorf

ttaccon

iatvygr

rai srianstcee

ruthstup

Q Rearrange the letters to give some words

to do with mass and weight.

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CEFOR

RIYTVAG

MAOIGLKR

WNOTEN

5.4 Battle of the forces

Starter question

Aims

• List forces that act on objects. [Level 4]

• Describe balanced and unbalanced forces. [Level 5]

• Explain the consequences of unbalanced forces acting on an object. [Level 6]

5.4 Battle of the forcesQuestions

1. What three things can happen to an object if the forces acting on it are unbalanced?

2. Copy and complete the sentences below using these words:constant length balanced

directions still

When two forces are equal in size but opposite in direction, they are called _______ forces. If the forces on an object are balanced, it willstay _______ or move at a _______ speed. If forces are balanced, force arrows will be the same _______ but point in opposite _______.

(Level 3)

(Level 3)

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5.4 Battle of the forcesQuestions

3. Use a force arrow diagram to show a radio-controlled car moving with a force of 3 N, with a friction force of 1 N. Use a scale of 1 cm = 1 N.

4. If a car is speeding up and the engine force is 250 N, what can you say about the size of the air resistance and friction?

5. Why can the weight of a car and its engine force never be balanced?

6. What do you think will happen to the speed of a space ship if it turns off its engines in space? Explain your answer.

(Level 4)

(Level 5)

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(Level 6)

(Level 7)

5.4 Battle of the forcesQuestions

7. A sports car and a van that have the same mass are travelling at the same speed. The van’s engine needs to produce more force than the car. Why is this?

(Level 7)

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