1.3 Ramps

1.3 Ramps - Observations About Ramps • • • • •...

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1 Phy 1405 1 Key Concepts: 1. Newton’s 3 rd Law 2. Support Force 3. Work 4. Energy Phy 1405 2 • Lifting an object straight up is often difficult • Pushing the object up a ramp is usually easier • The ease depends on the ramp’s steepness • Shallow ramps require only gentle pushes • You seem to get something for nothing Observations About Ramps Phy 1405 3 4 Questions about Ramps • Why doesn’t the cart fall through the ramp? • Are both cart and ramp pushing on each other? • Why is it easier to push the cart up a ramp? • Is there a physical quantity that’s the same for any trip up the ramp, regardless of its steepness? Phy 1405 4 Question 1 Why doesn’t the cart fall through the ramp? – Why doesn’t a ball fall through a table? – Is the table pushing up on the ball? – How can an upward push prevent falling? Phy 1405 5 Support Forces • A support force – prevents the ball from penetrating the table’s surface – points directly away from the table’s surface • Forces along surface are friction ( ignore for now) Phy 1405 6 Forces are Vectors Directions are Important Force #1 Force #1 Force #2 Force #2 Total Force Total Force = 0 Net Force • The sum of all forces on an object. • Determines object’s acceleration.
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2 Phy 1405 7 Adding up the Forces • As it sits on the table, the ball experiences – its weight downward – a support from the table upward • Since the ball isn’t accelerating, – the sum of forces (i.e., net force) on the ball is zero – the support force must balance ball’s weight! • Since cart isn’t accelerating into ramp, – the ramp’s support force must keep cart on surface W=mg F support Phy 1405 8 Clicker Question 1 A ramp makes lifting a box easier because… A) You can use less energy to lift the box B) The ramp exerts some force on the box C) A ramp lets you use wheels Phy 1405 9 Question 2 Are both cart and ramp pushing on each other? – Are both ball and table pushing on each other? – Is the table pushing on the ball?
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This note was uploaded on 02/07/2010 for the course PHY 1405 taught by Professor Russell during the Fall '07 term at Baylor.

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1.3 Ramps - Observations About Ramps • • • • •...

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