Phys ic s 1 4 4 – Vaishnav
Ho w T hing s Wo r k
Ho m e wo r k Se t # 1
Chapt e r 1 , Exercise 2 (p. 38):
As you jump across a small stre am, doe s a horizontal
force keep you moving forward?
What is that force ?
No—once you are in the air, no force acts on you.
You are carried forward by inertia.
Chapt e r 1 , Exercise 4 (p. 38):
Why doe s tapping your toothbrush on the sink dry it
Water is slipper y and is not held to the toothbrush by much friction.
When the toothbrush stops, very
little force acts on the water, which keeps moving forward due to inertia.
Chapt e r 1 , Exercise 6 (p. 38):
An unse atbe lte d drive r can be injure d by the ste e ring
wheel during a head-on collision.
Why does the driver hit the steering wheel when the
car comes to a stop?
Before the crash, car, seat, and driver are all moving forward.
A force acts on the car and stops it.
Howev er i f the driver is not wear ing a seat belt, he or she is not attached to the car, which then exer ts no
di r ec t force on the driver ’s upper body.
So due t o i t s i ner t i a, the driver ’s upper body keeps moving
forward, even when the car has stopped.
Problem 2 :
As part of Lab #1 , e ach pe rson in the class counte d the total numbe r of
M&M’ s in h is o r h e r o w n b a g .
There were 23 bags counted, and the individual results
56, 56, 58, 60, 57, 59, 57, 55, 59, 59, 55, 58, 58, 59, 60, 61, 58, 58, 58, 57, 57,
60, 59 .
Calc ulat e t he e xpe rime nt al me an, t he s t andard de viat io n, and t he s t andard de viat io n o f
You don’t have to show all your calculations here, but you do need to
explain (with words or with equations) how you calculated each of the requested
Since we’re talking about numbers of M&M’s, round your final answers to
the tenths place (i.e you would round 2.413 to 2.4).
Usi ng the same techni ques as i n the l ab, I cal cul ated the exper i mental mean by addi ng up al l the val ues
and then dividing by the total number ( in this case, 2 3 ) to obtain 5 8 .
To calculate the standar d
devi at i on, I t ook eac h of the individual values, subtracted the experimental mean from them, and took the
aver age of those number s.
Then, I took the squar e r oot of the aver age to obtain 1 .5 6 , which I r ounded to
To get the standard