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9 Cards in this Set
- Front
- Back
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What happens to the speed of when an object falls
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it gets increasingly faster, as their weight pulls them down to the centre of the earth
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How does streamlining reduce friction
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Streamlining an object makes a path for the air around the object instead of bringing the object directly against it. This results in reduced air resistance.
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Explain modifications lorries have to reduce air resistance
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They have deflectors at the front and back so that air can pass over the lorry instead of smashing into lots of air particles
Cover on the underside and wheels to reduce air resistance |
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What is terminal speed
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When all forces acting upon an object are equal, and so stays in its ate of motion
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How can a skydiver change their terminal speed
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If they go head down with their arms by their sides, the air resistance is reduced. Their speed increases until a new, faster terminal speed is reached
If they are spread-eagled, the air resistance is increased. Their speed decreases until a new, slower terminal speed is reached. |
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Why do cars have a top speed
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It's the terminal speed when the driving force from the engine is at its maximum. As the driving force from the engine increases, the speed of the vehicle will increase but so will air resistance
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Explain how the forces balance when a skydiver opens a parachute
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When the skydiver jumps out of the plane he accelerates due to gravity
As he speeds up, air resistance force increases, he carries on accelerating as long as the air resistance is less than his weight When the canopy opens it has a large surface area which increases the air resistance, this unbalances the forces and causes the parachutist to slow down As the parachutist slows down, his air resistance gets less until eventually it equals the downward force of weight. Once again the forces balance and he falls at terminal speed, but this time much slower than his terminal speed before |
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What affects the rate of falling
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Mass
Surface area Acceleration due to gravity |
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How does wiehgt affect the rate of falling
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The mass of an object and the acceleration due to gravity determine the weight of an object. This affects the amount of air resistance needed to balance its weight, which in turn depends on the speed of the object and its surface area
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