409674
Description
Flashcards by Anna Hollywood, updated more than 1 year ago
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Created by Anna Hollywood
over 10 years ago
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| Question | Answer |
| Increasing the speed reduces... | ...the time needed to cover the same distance |
| On a distance time graph, what does a steeper gradient mean? | A higher speed |
| What does a straight line on a distance-time graph indicate? | That the speed is constant |
| What does a curved line on a distance-time graph indicate? | That the speed is changing |
| What is a change of speed per unit of time called? | Acceleration |
| The area under a speed-time graph is equal to what? | The distance travelled |
| Is velocity a vector or a scalar? | Vector (both size and direction) |
| How do you work out the relative velocity for two cars that are moving in the same direction? | Find the difference |
| How do you work out the relative velocity for two cars that are moving in different directions? | The sum of the individual velocities |
| Why is a vehicle going round a roundabout accelerating? | It has to apply force towards the centre of the circle to keep changing direction |
| If the forces are balanced at what state is the vehicle? | Constant speed or rest |
| What are the 4 things that increase reaction time for a driver? | If they are... tired, under the influence of alcohol/drugs, travelling faster or distracted |
| What are the 3 things that increase braking distance? | -Poor road conditions -Worn brakes -Speed is increased |
| What are the 3 things that ensure safe driving? | -Keeping distance between you and other vehicles -Different speed limits -Slow down in poor conditions |
| What are the 5 factors that affect braking distance? | -Bigger mass=increased BD -Higher speed=increased BD -Worn breaks=increased BD -Worn tyres=increased BD -Increased breaking force=reduced stopping distance |
| What increases linearly with speed? | Thinking distance |
| What increases as a squared relationship? | Braking distance |
| When is work done? | When a force moves an object in the direction in which the force acts |
| What is weight a measurement of? | The gravitational attraction on a body acting towards the centre of the Earth |
| What is power? | The rate at which work is done |
| A persons power is greater when they run than when they walk. True or false? | True |
| What does the power rating of a car depend on? | Its engine size |
| How does the braking distance of a car increase? | With increasing speed (but not proportionally) |
| What happens to a car's K.E when it stops? | It changes into heat in the brakes, tyres and road. |
| Work done by brakes= | Loss in K.E |
| Braking force x braking distance = | Loss in K.E |
| What happens to the K.E and the braking distance when the speed of the car doubles? | They quadruple |
| What are the 5 factors that affect the fuel consumption of a car? | -amount of energy needed to increase its K.E -Amount of energy needed to do work against friction -speed -how it's driven -road conditions(rough) |
| What are 4 issues with electric cars (solar powered and battery driven)? | -Battery is large -Limited range before they need recharging -Expensive to buy -Rely on sun |
| What are two advantages of electric cars? | -They don't (directly) pollute -Cost of recharging is low |
| How do battery powered cars indirectly pollute? | Recharging the batteries requires electricity from power stations which pollute |
| Although biofuels may reduce carbon emissions, why is this not certain? | Because deforestation leads to an increase in CO2 levels |
| What spreading momentum change over a long time do? | Reduces the force |
| How can we reduce acceleration (and therefore force)? | -Increasing stopping/collision time -Increasing stopping/collision distance |
| What are the 5 features that reduce acceleration? | -Crumple zones -Seat belts -Air bags -Crash barriers -Escape lanes |
| What do modern cars have that help absorb energy in a crash (4 things)? | -Brakes that get hot -Crumple zones that change shape -Seat belts that stretch -Air bags that inflate and squash |
| Why does seat belts stretching help absorb energy? | Converts K.E into elastic energy |
| What are the 3 reasons why drivers don't like wearing seatbelts? | -Risk of chest injury -Could be trapped in fire -Could encourage driver to drive more carelessly as he/she knows they're protected by seatbelt |
| What is the best way to gain safety information? | By using crash tests with real vehicles and dummies |
| What are ABS brakes? | A primary safety feature which helps to prevent a crash |
| How does the ABS system work? | Wheel-speed sensors send information to a computer about the rotational speed of the wheels. The computer controls the pressure to the brakes to prevent the wheels locking up. This increases the braking force just before the wheels start to skid |
| What are two other primary safety features? | -Cruise control (stops a driver becoming tired and pressing harder on the accelerator) -Electric windows and paddle shift controls (allows driver to concentrate on road) |
| What are the two things that affect the size of air resistance? | Cross sectional area and speed |
| When does air resistance only have effect? | When it is large compared to the weight |
| What is the journey of a parachutist like in terms of forces? | 1)Accelerates, displacing more air molecules a second. Air resistance increases, reducing his acceleration 2)Weight and air resistance are equal = terminal speed 3)Parachute opens and air resistance increases due to large surface area. Parachutist decelerates and air resistance decreases 4)New lower terminal speed |
| What are three qualities of the gravitational field strength? | -Unaffected by atmospheric conditions -Varies with position on the Earth's surface -Varies with height above/below Earth's surface |
| What does an object held above the ground have? | Gravitational potential energy |
| What are the 4 steps of a bouncing ball? | 1)Ball has GPE but no K.E 2)Reached ground-has K.E but not GPE 3)Ball squashes-has EPE-converted to K.E as it leaves ground 4)At top of bounce has GPE |
| What is the loss in GPE in a skydiver due to? | The work against friction (air resistance) |
| change in GPE = | work done against friciton |
| What do the riders at the top of a roller coaster ride have? | GPE |
| What happens when the roller coaster is released? | Converts GPE into KE as it falls |
| Loss in GPE= | Gain in KE |
| Why does each peak in a roller coaster have to be lower than the one before? | Because some energy is transferred to heat and sound due to friction and air resistance |
| GPE at top of roller coaster= | KE at bottom + energy transferred due to friction |
| If speed doubles what happens to KE? | It quadruples |
| If mass doubles, what happens to KE? | It doubles too |
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