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| Questão | Responda |
| What two words together mean 'two forces that arise from the same interaction'. | interaction forces |
| Two properties of an interaction pair always remain the same. What are they? | The two forces are always equal in size and opposite in direction. |
| What is the name for the force that arises from two objects touching? | Contact forces. |
| What is action-at-a-distance? Give two examples. | The forces that sometimes occur between objects that aren't touching - such as a magnetism and gravity. |
| What are the two properties of action-at-a-distance forces that are different from contact forces? | Action-at-a-distance forces act all the time, but grow weaker with distance. |
| How do objects, such as cars, get moving? | An interaction force between them, such as a car's wheels turning and the ground pushing the wheels in response. |
| If a car is stuck on ice it doesn't move. Why is this? | There's no friction, which stops car wheels from slipping. |
| What causes friction? | The roughness of two surfaces sliding past one another. The grooves in one surface interlock with the grooves in another. |
| What two things does the amount of friction depend on? | The weight of the box and the roughness of the two surfaces. |
| What is the sum of all objects acting on an object called? | The resultant force. |
| What is 'the force exerted by a hard surface on an object that presses on it'? | The 'reaction' of the surface. |
| Describe the phases that occur when a ball is dropped in freefall. (3 phases) | 1. The ball is released and begins falling. 2. It's speed steadily increases, so it has a steady acceleration. 3. It lands and it's reaction of the surface causes it to bounce with equal and opposite force. |
| What 4 factors affect air resistance? | Larger mass, larger surface area, faster movement and more air particles per cm cubed increases air resistance. |
| What is the difference between distance and displacement? | Distance is how long a journey is, whilst displacement is how far the end point is from the start point. |
| What two words mean 'the speed of an object at a given moment' and how is this worked out? | instantaneous speed is measured by taking a short time interval and measuring the average time for that. |
| In a distance-time graph, what does a slope, a curve and a horizontal line mean? | Slope means steady speed, a curve means acceleration or deceleration and a horizontal line means the object isn't moving. |
| When is it possible to draw a displacement-time graph? | When an object moves in a straight line. |
| What makes a displacement-time graph and a distance-time graph different? | The direction of motion - if an object travels in one direction the two graphs are the same, if the objects reverses direction the two graphs are different, and displacement shows this but distance doesn't. |
| What does a slope, a curve and a horizontal line mean on a speed-time graph? | A slope means acceleration or deceleration at a constant rate, a curve means acceleration or deceleration at an inconstant rate and a horizontal line means a steady speed. |
| How does a velocity-time graph show when an object begins travelling in the opposite direction? | The line of the graph becomes negative. |
| What does a force acting upon an object cause? | A change in motion. |
| What's the equation that works out momentum? | momentum = mass x velocity |
| Why do crumple zones on cars work? | The change of momentum is fixed, so when the time the crash takes increases the resultant force has to decrease to equal the same change of momentum. |
| Aside from crumple zones, name two other safety features used in cars and motorcycles. | Motorcycle helmet and car seatbelts. |
| If a resultant force on an object is 0N, what happens to the object? | Nothing - if it's not moving it doesn't move, and if it's already moving it continues at the same speed. |
| What is the force pushing an object forwards called? | driving force |
| What are forces such as air resistance and friction called? | counter-force(s) |
| What is the energy of a moving object called? | kinetic energy |
| What's the equation that explains how work done by a force is calculated? | work done by a force = force x distance moved in the direction of the force |
| When an object is moved vertically upwards, what does it gain? | gravitational potential energy (GPE) |
| What's the equation for GPE, with units? | GPE (joules, J)= weight (newtons, N) x vertical height difference (metres, m) |
| What's the equation for kinetic energy, with units? | kinetic energy (joules, J) = 1/2 x mass (kilograms, kg) x velocity squared (metres per second, m/s) |
| What is the idea that 'energy is never used up, just passed on to another object' called? | conservation of energy |
| What happens when gravitational energy decreases? | kinetic energy decreases (and vice versa) |
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