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11 Cards in this Set
- Front
- Back
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What is weight? |
Weight is not the same as mass. Mass is a measure of how much stuff is in an object. Weight is a force acting on that stuff.You have to be careful. In physics, the term weight has a specific meaning, and is measured in newtons. Mass is measured in kilograms. The mass of a given object is the same everywhere, but its weight can change. |
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Explain what gravitational field strength is and what are the gravitational field strength of the earth and moon? |
Weight is the result of gravity. The gravitational field strength of the Earth is 10 N/kg (ten newtons per kilogram). This means an object with a mass of 1kg would be attracted towards the centre of the Earth by a force of 10N. We feel forces like this as weight.You would weigh less on the Moon because the gravitational field strength of the Moon is one-sixth of that of the Earth. But note that your mass would stay the same. |
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How do you calculate weight? |
weight (N) = mass (kg) × gravitational field strength (N/kg) |
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What are the forces acting on a falling object? |
1. The weight of the object. This is a force acting downwards, caused by the object’s mass the Earth’s gravitational field. 2. Air resistance. This is a frictional force acting in the opposite direction to the movement of the object. |
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What are the three stages of falling? |
1. At the start, the object accelerates downwards because of its weight. There is no air resistance. There is a resultant force acting downwards. 2. As it gains speed, the object’s weight stays the same, but the air resistance on it increases. There is a resultant force acting downwards. 3. Eventually, the object’s weight is balanced by the air resistance. There is no resultant force and the object reaches a steady speed, called the terminal velocity. |
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Explain what the term 'terminal velocity' means. |
As the feather falls, its air resistance increases until it soon balances the weight of the feather. The feather now falls at its terminal velocity. But the coin is much heavier, so it has to travel quite fast before air resistance is large enough to balance its weight. In fact, it probably hits the ground before it reaches its terminal velocity. |
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What is 'thinking distance'? |
It takes a certain amount of time for a driver to react to a hazard and start applying the brakes. During this time, the car is still moving. The faster the car is travelling, the greater this thinking distance will be. |
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What are some factors affecting thinking distance? |
The thinking distance will also increase if the driver's reactions are slower because they are: under the influence of alcohol under the influence of drugs tired |
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What is breaking distance? |
The braking distance is the distance the car travels from where the brakes are first applied to where the car stops. If the braking force is too great, the tyres may not grip the road sufficiently and the car may skid. The faster the car is travelling, the greater the braking distance will be. |
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What factors increase breaking distance? |
The braking distance will also increase if: The brakes or tyres are worn. The weather conditions are poor, such as an icy or wet road. The car is more heavily laden, for example, with passengers and luggage. |
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What is stopping distance? |
The stopping distance is the thinking distance added to the braking distance. |
