Physics 1B03summer-Lecture 13 Final Exam Wed April 18 – 2pm – check the schedule for rooms! 2...

Physics 1B03summer-Lecture 13

Final Exam

Wed April 18 – 2pm – check the schedule for rooms!

2 hours long – 30 MC questions

Covers all material with approximately equal weight, up to and including the final lecture on fluids.

Review questions will be posted on the website later today !


Office Hours

I’ll be in my office between 12-2pm on these days (posted on the website):

• Tuesday Apr 10

• Wednesday Apr 11

• Tuesday Apr 17

• Wednesday Apr 18 (11am – 1pm)


Uncertainty

Assume that a is related to measurable quantities , F, m and θ

by Fsinθ=ma. The absolute uncertainty in a is:


Example 1

AF

n

gF

f

!@%&*#$

You are pushing a 50kg block with a force of 100 N over a surface with μs=0.15 and μk=0.1. With what force does the block push back on you ?

Ans: 49N


Example 2

AF

n

gF

f

!@%&*#$

You are pushing a 50kg block with a force of 100 N over a surface with μs=0.15 and μk=0.1. What is the work done by the force of friction if you push the block for 5m ?

Ans: -245J


Example 3

A block of 3kg is pushed with a force FA=40N at an angle of 45 degrees to the horizontal. If μk = 0.1, find the acceleration.

m

θ

FA


Projectile Motiony=voyt-½gt2

x

yvo

x=voxt

- resolve motion into x/y - x and y position equations - x and y velocity components


Concept Quiz

A tennis ball is placed on top of a basketball and both are dropped.The basketball hits the ground at speed v0. What is the maximum speed at which the tennis ball can bounce upward from the basketball? (For “maximum” speed, assume the basketball is much more massive than the tennis ball, and both are elastic).

a) v0

b) 2v0

c) 3v0

?

v0

v0-elastic collision-relative velocity


Example 3• A 100 g baseball is thrown with a speed of 10m/s. It is hit straight back toward the pitcher at a speed of 30m/s. The

interaction force is shown by the graph:

What is the maximum force Fmax that the bat exerts on the ball ?

Fmax

6mst

F


Example 5

A bullet of mass m moving with velocity v is shot into a block of mass M that is at rest on the edge of a table. If the bullet embeds in the block, determine the velocity of the system.

How far would the system fall if it was sitting at the edge of a

table of height h ? – use projectile motion !


Gravitational Work

s2 y s1

mg When the block is lowered, gravity does work.

The work done is path independent !!! So, in bothcases it is:

W=mgs1=mgs2


Example 7

v0A block of mass m = 2.0 kg starts to slides at speed v0 = 3.0 m/s on a table with μk=0.1. After 5m it hits a spring with k = 400 N/m.

If at the point the block hits the spring the friction is gone, how far will the spring compress before the block stops?


Constructive Interference:

Δr = m λ m = 0, ±1, ±2, …

mt

mL

dy

2

<- for double slit

<- for thin film

Remember: low to high, phase shift of pi (=λ/2) also, don’t forget ‘n’ -> λ/n


Destructive Interference:

Δr = (m + ½)λ m = 0, ±1, ±2, …

)2

1(2

)2

1(

mt

mL

dy <- for double slit

<- for thin film

Remember: low to high, phase shift of pi (=λ/2) also, don’t forget ‘n’ -> λ/n


Example 8

What is the minimum thickness of a layer of gasoline (n 1.3) floating on water (n=1.5) needed to produce destructive interference for light with a 500nm wavelength ? (air : n 1.00).

Physics 1B03summer-Lecture 13 Final Exam Wed April 18 – 2pm – check the schedule for rooms! 2...

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