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Forces and Elasticity

• Using forces to compress or stretch objects causes the object to deform (change shape)
• Springs are special as they go back to their original shape once the force has been removed.
• Energy transfer (see above) = work done
• Work is done when an object is deformed due to a force.

• Spring:

1. Stretching a spring means work is being done as energy is being transferred

2. Energy transfers from kinetic energy stores → elastic energy stores

3. When force is removed the spring goes back to original shape so, energy transferred back to its kinetic energy store.

• Hooke’s Law = the amount a spring stretches (extension, e) is directly proportional to force applied (F).
• Some objects obey Hooke’s Law (springs) but this law only applies up to a certain force.
• F = k X e
• K is the spring constant. The value of it depends on the material you are stretching. (Newton per metre N/m)
• Equilibrium = all forces are balanced
• If a stretched/compressed spring holds a weight still = force of weight = force of the spring. Forces are balanced = equilibrium

How long have you…? (present perfect 4) Exercises

Use the information given to create questions beginning with ‘How long…?’

• It is snowing.

• The weather is shining.

• John and Kate are married.

• My brother has gone on holiday.

• My aunty and uncle live in Canada.

• My sister is a teacher.

• I work at the chemist.

• I’ve known Susan since I was a baby.

• Jonathan is learning to speak to Mandarin.

Fill in the missing gaps in the sentences using the present perfect (=has/have + past participle)

• I have known Kate a long time.

• My brother has been playing the piano he was 11 years old.

• My mum and dad on holiday to America. They

gone since last Sunday.

• I Ben and Emma since primary school.

We to the same primary and secondary school.

• My sister learning to speak French because she
is going to France next month.

Use the appropriate words in the missing gaps.

have you lived       lives      to

has been       works        have known

I have bought       have worked.

• My sister in Spain. She is studying Spanish

with her friend Rosie. I Rosie since I was 5.

• Spencer like with Jamie. They have worked

together for 2 years.

• How long in Australia?

• a new dress for prom.

• He to Thorpe park.

Challenge: Create 4 of your own questions beginning with ‘How long……?’

1.

2.

3.

4.

1 2 3 4 5 6

“Every accomplishment starts
With the decision to try.” Gail Dever

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