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Physics
Motion and Forces (Paper 1)
| Question | Answer |
|---|---|
| What is a Scalar Quantity? | A quantity that only has a magnitude. |
| What is a Vector Quantity? | A quantity with a magnitude and a direction. |
| How can a Vector Quantity be represented? | With Vector arrows |
| How do vector arrows represent vectors? | Length represents magnitude, points in direction. |
| Give 3 examples of vectors. | Force, Velocity and Displacement |
| Give 6 examples of scalars. | Time, speed, temperature, mass, distance and energy |
| What is velocity? | Speed of an object in a specific direction |
| Give an equation relating average speed, distance and time. | Speed= Distance/Time |
| On a distance/time graph , what value does the gradient of the line represent? | The speed |
| On a displacement/time graph , what value does the gradient of the line represent? | The velocity |
| What must be done to calculate speed at a given time from a distance-time graph for an accelerating object? | Draw tangent to the curve at req time and calculate gradient of tangent |
| Give the equation for acceleration. | Change in velocity/time taken |
| Give an equation relating final relating final velocity with initial velocity, displacement and acceleration. | v²=u²+2as |
| How can the distance travelled by an object be calculated from a velocity-time graph? | It is the area under the graph |
| On a velocity/time graph, what does the gradient of the graph represent? | The acceleration |
| State a typical value for the speed of sound. | 330m/s |
| What is typical value for human walking speed? | 1.5m/s |
| What is typical value for human running speed? | 3m/s |
| What is a typical value for human cycling speed? | 6m/s |
| Give approx value for the acceleration of an object in free fall under gravity near the Earth's surface. | 10m/s² |
| What is the name given to the single force that is equivalent to all other forces acting on a given object? | The resultant force |
| State Newton's first law for a stationary object. | If the resultant force on a stationary object is 0, the object will remain at rest |
| State Newton's first law for a moving object. | If the resultant force on a moving object is 0, the object will continue moving at the same velocity |
| State the defining equation for newtons second law. | Resultant Force= Mass x Acceleration (F=ma) |
| State Newton's second law in words. | An objects acceleration is directly proportional to the resultant force acting on it and inversely proportional to its mass |
| What is weight? | The force that acts on an object due to gravity and the object's mass |
| State the equation for weight. | Weight = Mass x Gravitational Field Strength |
| What Unit is used for weight? | N |
| Unit used for gravitational field strength? | N/kg |
| What piece of equipment can be used to measure an object's weight? | Calibrated spring-balance or newton-meter |
| When can an object travelling at a constant speed not have a constant velocity? | When the object is changing direction (eg. moving in circle) |
| Why does an object travelling at a constant speed in a circle not have a constant velocity? | Speed is scalar, velocity is a vector quantity, direction is constantly changing and therefore so is velocity |
| What is the resultant force that acts on an object moving in a circle called + which direction does it act? | Centripetal force and it acts towards centre of the circle |
| What is inertial mass? | A measure of how difficult it is to change an objects velocity (ratio of force over acceleration) |
| Sate Newton's third law. | Whenever two objects interact, the forces they exert on each other are always equal and opposite |
| What is the equation for Momentum? | Mass x Velocity |
| What is the unit used for Momentum? | kgm/s (Kilogram meters per second) |
| In a closed system, what can be said about the momentum before and after a collision? | The total momentum before and after are equal |
| State an equation linking change in momentum, force and time. | Force x Time = Change in Momentum |
| Give the 5 steps to measure human reaction time. | Use ruler drop test, Person A and B hold each end of ruler with 0cm mark at bottom, Person A drops the ruler without telling, Person B catches it, the distance travelled corresponds to their reaction time |
| Why is it important the 0cm mark is at the bottom? | So you can obtain the distance directly |
| How do you work out stopping distance of a vehicle? | Thinking distance + Braking distance |
| For a given braking distance, if speed is increased, how does that affect stopping distance? | Increase in speed increases the stopping distance |
| Give a typical range of values for human reaction time. | 0.2 seconds - 0.9 seconds |
| Give three factors which can affect a drivers reaction time. | Drugs, Alcohol and Tiredness |
| Give two factors which may affect braking distance. | Wet/icy road conditions and Poor tyre/brake conditions |
| Describe the energy transfers that take place when a car applies it's brakes. | Work is done by the friction force between the brakes and the wheel. KE of the wheel is converted to heat and is dissipated to the surroundings through the brake discs |
| To stop a car in a given distance, if velocity is increased, what must happen to the braking force applied? | The braking force must also be increased |
| State two consequences of a vehicle undergoing very large decelerations. | KE converted to heat is very high causing brakes to overheat & Loss of control of the vehicle |
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