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Friction and Resistance

Friction is a force acting in the opposite direction to movement. Friction is the force that tries to stop objects sliding past each other. It needs to be overcome if you want to push an object out of way.

Friction is good because:

• Allows things to stop and start
• Allows tyres to grip on the road
• Also acts as brakes

• Slows you down.
• Wastes energy – friction between moving parts generates heat which is a waste of energy.
• Limits top speed – air resistance takes most of energy so limits the fastest speed you can achieve.

Air/water resistance push against objects moving in air/water. They try to slow objects down so are a frictional force.

To go faster, the shape of objects need to be streamlined. Therefore, they slip through air/ water without much resistance acting against them.

How air resistance affects a parachutist?

1. At the start, the parachutist only has the force of its weight pulling it down, so it moves faster

2. Due to the increasing speed, air resistance in the opposing direction increases.

3. When the parachute opens, air resistance increases as there is a larger surface area (due to the parachute opening). The parachutist loses speed and slows down slowly.
4. The forces become balanced when air resistance equals the weight. Overall force is zero= strong steady speed
5. Once the parachutist on the ground, the weight acting downwards is equally opposed (balanced) by an upward force.

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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