GENERAL PHYSICS I Math. Edu. Program

1. GENERAL PHYSICS IMath. Edu. Program Yohanes Edi Gunanto TC - UPH

2. System of Particles, Collisions Momentum and Impulse

3. Quantity of Motion DEFINITION II Newton’s Principia • The quantity of motion is the measure of the same, arising from the velocity and quantity of matter conjointly. • The motion of the whole is the sum of the motions of all the parts; and therefore in a body double in quantity, with equal velocity, the motion is double; with twice the velocity, it is quadruple.

5. Checkpoint Problem • Consider two carts, of masses m and 2m, at rest on an air track. If you push first one cart for 3 s and then the other for the same length of time, exerting equal force on each, the momentum of the light cart is 1. four times 2. twice 3. equal to 4. one-half 5. one-quarter the momentum of the heavy cart.

7. Systems and Conservation of Momentum

9. Checkpoint Problem: Choice of system • Drop a stone from the top of a high cliff. Consider the earth and the stone as a system. As the stone falls, the momentumof the system • 1. increases in the downward direction. • 2. decreases in the downward direction. • 3. stays the same. • 4. not enough information to decide.

15. External Forces and Change of Momentum Vector • The external force may be zero in one direction but not others • The component of the system momentum is constant in the direction that the external force is zero • The component of system momentum is not constant in a direction in which external force is not zero

16. Check point Problem : Acrobat and Clown • An acrobat of mass mAjumps upwards off a trampoline with an initial y-component of velocity vy,0= v0. At a height h0, the acrobat grabs a clown of mass mB. Assume the acrobat grabs the clown during a time interval that is negligibly small. a) What is the velocity of the acrobat immediately before grabbing the clown? b) What is the velocity of the acrobat immediately aftergrabbing the clown? c) How high do the acrobat and clown rise?

17. Collision Theory

18. Collisions • Any interaction between (usually two) objects which occurs for short time intervals Δt when forces of interaction dominate over external forces. • Of classical objects like collisions of motor vehicles. • Of subatomic particles – collisions allow study force law. • Sports, medical injuries, projectiles, etc.

20. Check point Problem: totallyinelastic collision • A car of mass mA moving with speed vA1 collides with another car that has mass mB and is initially at rest. After the collision the cars stick together. What is the change in mechanical energy due to the collision?

23. Particle Collisions: ProblemSolving Strategies

24. Two Dimensional Collisions:Momentum Flow Diagram • Consider a collision between two particles. In the laboratory reference frame, the ‘incident’ particle with mass m1, is moving with an initial given velocity v1,0. The second ‘target’ particle is of mass m2 and at rest. After the collision, the first particle moves off at an angle θ1,f with respect to the initial direction of motion of the incident particle with a final velocity v1,f. Particle two moves off at an angle θ2,f with a final velocity v2,f. Draw a momentum diagram representing this collision. Answer:

28. THANKS