Position is specified by x (or x and y in two dimensions)

1. Position is specified by x (or x and y in two dimensions) Displacement is change in position Dx = xf - xi Average velocity is displacement divided by time interval vave = Dx/Dt a vector Distance travelled is length of path Average speed is distance travelled divided by time interval a scalar Instantaneous velocity is limit of velocity as time interval Dt approaches 0 V = lim Dx/Dt xf = xi + vt If velocity is constant

2. Average Acceleration is change in velocity divided by time interval aave = Dv/Dt a vector Instantaneous acceleration is limit as time interval Dt approaches 0 a = lim Dv/Dt If acceleration is constant vf = vi + at xf = xi + vit + ½ a t2 vf2 = vi2 + 2 a (xf- xi)

3. The UW is hosting a Public Lecture series on sustainable energy in the Spring quarter. The lectures will address: *Solar power (Thursday April 1 at 6:30 PM Kane Hall ) *National- and Global-scale planning for sustainable energy *The next generation of nuclear power plants in the U.S. *Genetically-engineered organisms for biofuel production *The environmental impact of sustainable energy projects Full details are at http://courses.washington.edu/efuture Details for the 1-2CR seminar course, which will cover a wider range of topics, are at: http://courses.washington.edu/efuture/academic.html Contact Jerry Seidler at efuture@uw.edu with any questions.

4. Problem 2-83 Parameters: deceleration a = -7 m/s2 reaction time tR = 0.5 stopping distance d = 4 m Initial velocity v Distance travelled during reaction time xR = v tR Distance travelled during breaking time = xB d = xR + xB Relation between xB and initial velocity v2 = 2 |a| xB xB= ½ v2 /a d = xR + xB = vtR + ½ v2/a v2 +2a tR v – 2a d = 0

5. A projectile is fired at If air resistance is neglected, the line in the graph that best represents the horizontal displacement of the projectile as a function of travel time is an angle of 45º above the horizontal A) 1 B) 2 C) 3 D) 4 E) None of these is correct

6. target y1T yT = y1T-1/2 g t2 = xT tan q - 1/2 g t2 q xT projectile yP = vyP t -1/2 g t2 = (vP sin q) t - 1/2 g t2 xP = vxP t = (vP cos q) t t = xP/(vP cos q) yP = (vP sin q) xP/(vP cos q) - 1/2 g t2 = xP tan q- 1/2 g t2 Conclusion: when xP = xT yP = yT

7. A particle is moving. At t=0 the velocity vector is v1 A little later the velocity vector is v2 v1 v2 The magnitudes are the same: |v1| = |v2|. The change in velocity is approximately: B A D C E. zero

8. A particle is moving clockwise around a circle with constant speed. The acceleration vector points inward. Suppose the particle were moving Counter- Clockwise. The acceleration vectorpoints: • Inward • Outward

9. L is length of a chord; s is arc length s L q R s = R q The circle has radius R Approximately L = R q where q is in radians A particle is moving around a circle with speed v: ds/dt = R dq/dt = R w Speed is ds/dt so v = R w

10. A baseball is thrown horizontally with an initial speed v. How far has it dropped after moving horizontally through a distance L? • ½ g L/v • ½ g v/L • ½ g (L/v)2 • ½ g (v/L)2 • 2 g L/v

11. M q How large is m if system is in equilibrium? m • m = M • m = M / sin(q) • m = M sin(q) • m = M cos(q) • M = M / cos(q)

12. box v Truck is moving with speed v and starts to decelerate with acceleration -a, Mass of truck is M, mass of box is m. What is direction of the force on box needed to keep the box stationary on the truck? A. forward B. backward What force on the box is needed to keep the box stationary on the truck? • ma • 0 • mg • (M+m)a

13. T2 = • m1a • (m1+m2)a • (m1+m2+m3)a • 0 • (m1+m2-m3)a

14. What horizontal force is required to move the block at constant speed? • Mg / sin q • Mg cos q • Mg sin q • Mg tan q • Mg / cos q

15. The mass is turned on its side so • contact area is smaller. • The force needed to overcome friction is: • Smaller • Larger • Same

16. A plane moves at constant speed v, • in a horizontal circle of radius r. • The plane is “banked” at an angle q, so that • The total force (gravity + normal force) • on a passenger of mass m, is upward from the seat. • Does the correct bank angle depend on m? • Yes • No

17. A block with mass m, is on a • horizontal surface having friction. • The block has initial velocity v0 • The block will eventually stop. • Does the distance travelled depend on m? • Yes • No

18. The work done in moving the box • up the ramp is • Mg L • Mg L Cos q • Mg L2 • Mg L Sin q • ½ Mv2

19. Mass m1 is at rest. An equal mass m2, moves with velocity v, and collides with it. The collision is INELASTIC. What is the final velocity of the mass m2? • 0 • v • v/2 • v/4 • v/Sqrt(2)

20. Mass m1 is at rest. An equal mass m2, moves with velocity v, and collides with it. The collision is ELASTIC. What is the final velocity of the mass m1? • 0 • v • v/2 • v/4 • v/Sqrt(2)

21. Non-clicker question: We assign k to a dielectric (E=E0 /k) A conductor has what value of k ?