Understanding Momentum and Kinetic Energy in Physics
Explore the concepts of momentum and kinetic energy in physics through discussions on solar-powered cars, calculation exercises, and safety features to minimize injury. Discover the relationship between mass, velocity, momentum, and kinetic energy in various scenarios.
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Presentation Transcript
Starter Starter Match the letter to the number A solar powered car 1 fuel comes from fossil fuels, and is easily available B petrol/diesel 2 are quiet cars but still contribute to global warming (power stations) C - electric 3 part electric and part fuel car D - hybrid 4 gets energy from the Sun
Objectives Objectives Know what momentum is Be able to calculate momentum Be able to use the KE equation
Homework Homework You final assessment will be on Friday Out of 20 As evidence of your revision, complete the A3 broadsheet you started last Thursday
Momentum Momentum A moving object has momentum. Momentum is the tendency of an object (something that has mass) to keep moving in the same direction. It depends on 2 things: mass (what something is made of) and velocity (speed in a particular direction). Which car has the greatest momentum? Which will be harder to stop? 50 m/s 100 m/s
Momentum = mass x velocity Momentum = mass x velocity Kg m/s m/s kg 1. Calculate the momentum of a toy train of mass 1.5 kg travelling at 0.2 m/s due west. 2. Which has greater momentum, a car of mass 1000 kg travelling at 32 m/s or a van of mass 1800 kg travelling at 20 m/s? 3. Calculate the momentum of a bullet of mass 15 g (0.015 kg) travelling north at 200 m/s. Extension: A fox with a mass of 1400g is running west. What is his momentum? Hint: look at the units!
Change in momentum Change in momentum Name some car safety features .. To minimise injury to people in a car, if we increase the change in momentum over a longer time we can decrease the force acting on them, and therefore less likely to be injured Force = change in momentum time
Calculating kinetic energy question Calculating kinetic energy question A car with a mass of 1,500 kg travels at a velocity of 20 m/s. What is the kinetic energy of the car? kinetic energy = x mass x velocity2 = x 1,500 x 202 = 300,000J = 300kJ
Calculating kinetic Calculating kinetic energy 1. If a lorry with a mass of 1350 kg is moving with a velocity of 15 m/s, what will it s KE be? 2. A football is moving north at 24 m/s. If the ball weighs 4 kg, how much KE does it have? 3. A charging rhinoceros of mass 800 kg is moving at 15 m/s. What is it s KE? 4. A 48 kg horse is galloping through a field at 50 m/s. How much KE does it have? Extension: If a mouse of mass 800 g is moving at a steady rate of 3 m/s, how much KE does it have? Hint: look at the units! energy
Mass vs weight Mass vs weight The weight of something is due to it s gravitational attraction towards Earth Mass is the stuff something is made up of To find the weight of something we multiply the mass (in kg) by the gravitational field strength of the Earth (in N/kg), which is 10 E.g. the weight of an object of mass 54kg = 54 kg x 10 N/kg = 540 N Weight (N) = mass (kg) x gravitational field strength - g (10N/kg) g = 10N/kg W = m x g
Mass vs weight Mass vs weight Calculate the weight of the following objects: Book of mass 0.5kg Chair of mass 7kg Laptop of mass 2.5kg Person of mass 60kg Extension: rubber ball of mass 800g
Plenary Plenary 1. What are the units of momentum? 2. What does KE stand for? 3. What are the units of weight? 4. What can we do to a person s momentum in the event of a car accident? 5. What is force measured in? 6. What are the units of KE?
