Physics 11 Advanced

Mr. Jean

May 9th, 2012

The plan:

• Video clip of the day

• Review of Last day’s inelastic situation

• Spring Application Question

Cold Fusion:

• Question #3: Wow this looks just like a test question.A 2.0 kg block is sliding on a smooth table top. It has a totally inelastic collision with a 3.0 kg block that is at rest. Both blocks, now moving, hit the spring and compress it. Once the blocks come to rest, the spring restores itself and launches the blocks. They slide off the right side of the table. The spring constant is 775 N/m. Find: – (a) the velocity of the two blocks after the collision. – (b) The distance the spring is compressed. – (c) The velocity of the blocks after they leave the spring. – (d) The distance the blocks travel before they hit the deck after the leave

the tabletop. – (e) The kinetic energy of the blocks just before they hit the deck.

1 .2 m

v = 10 .0 m /s

Solutions:

• C) If energy is conserved in the spring, they should have the same speed when they leave as they had going into the spring. So they should be moving at 4.0 m/s to the right.

• D) Distance they fall from table:

2

2

2 1.21 20.495

2 9.8

myy at t s

mas

4.0 0.495 2.0m

x vt s ms

• (e) The kinetic energy of the blocks at the bottom (just before they hit) must equal the potential energy at the top of table plus the kinetic energy the blocks had before they began to fall.

New: Application Problems

• A spring is compressed a distance of 12 cm by a 675 g ball. The spring constant is 225 N/m. The ball is on a smooth surface as shown (next slide). The spring is released and sets the ball into motion. – (a) the speed of the ball when it leaves the spring, – (b) the speed of the ball just before it leaves the edge of the

table, – (c) the kinetic energy of the ball just before it hits the deck,– (d) the horizontal distance, x, it travels when it leaves the table

until it hits the deck. Assume that the ball rolls down the ramp.– (e) What is the impact angle?– (f) What is the overall velocity at impact with the deck?

1 .0 m

1 .7 m

x

Solutions:

0 022

21 1 1

0.12 225 2.22 2 0.675

kg mk mkx mv v x m

m kg ss m

0 0 0 02 2 21 1 1

22 2 2

mv mgy mv v v gy

2

21

2 2.2 9.8 1.7 1.0 4.32f

m m mv m m

s ss

A)

B)

• C)

• D)

0 02 21 1

2 2mgy kx kx

0 0 2221 1

0.675 9.8 1.7 225 0.12 132 2

m NK mgy kx kg m m J

ms

2

2

2 1.01 20.452

2 9.8

myy at t s

mas

4.3 0.452 1.9m

x vt s ms

• E)

• F)

Through the Wormhole: “What are we made of?”

• Now that we are finishing up on conservation of energy laws we are going to move into light, waves and optics.

• We need a greater background on what these things are and in fact what scientists perceive matter to be.