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# Science P2 Topic 4

### Edexcel GCSE additional science physics: momentum, energy, work and power

What is the stopping distance and what is it made up of? The stopping distance is the distance covered from when you realise you have to stop to when the breaks bring the vehicle to a halt- it is made up of the thinking distance + the braking distance
What is the thinking distance and how do you calculate it? Thinking distance is the distance covered from when you realise you have to stop to when you react and hit the breaks- thinking distance = driver's reaction time X speed of vehicle
What is the braking distance? The distance covered from when the breaks are pressed to when they bring the vehicle to a halt
What factors affect the stopping distance? * driver's reaction time (affected by fatigue, drugs, illness) * condition of the road surface * condition of the tyre * friction between the tyre and road surface * speed of the vehicle * mass of the vehicle
What is momentum? The amount of mass in motion or how difficult it is to stop a moving object, measured in kg.m/s
Is momentum a vector or scalar quantity and why? A vector quantity as it has a size and a direction (the direction of the velocity)
What is the conservation of linear momentum? The idea that momentum is conserved at collisions
100kg skateboarder travels at 5m/s, crashes into stationary trolley with 10kg mass- if the skateboarder keeps going in the same direction at 2m/s, what is the speed of the trolley after the collision? 30 m/s
What are some examples of vehicle safety measures and what do they try to do? all vehicle safety measures try to reduce the rate of change of momentum to reduce the force of the crash on the passenger: seat belts, crumple zone, air bags
Why is bubble wrap used? It is used to pack fragile items as it decreases the rate of change of momentum when dropped, because the bubbles slowly compress, reducing impact
What is needed to change the momentum? A force (equal to the rate of change of momentum)
What is work? Work is done when energy is transferred from one form to another, measured in joules
What is power in relation to work? Power is the rate of doing work, measured in watts
1 watt = ? (in relation to work) 1 joule of work per second
how do you calculate how much work must be done to stop a vehicle? work done = braking distance X braking force
What is the work done to stop a moving vehicle equal to? The initial kinetic energy
What is gravitational potential energy? Energy that is stored due to an object’s position in a gravitational field
What is the strength of the gravitational field strength on earth? 10 N/kg
What is kinetic energy? Movement energy
For a falling object: the initial amount of gravitational potential energy = ? The kinetic energy when the object hits the ground
Created by: 11043