Midterm

Question 1

Which gives the relationship for kinetic energy?

Answer 1

KE = 1/2mv^2

proportion of 1/2 mass to the velocity squared

Question 2

Machines make tasks easier by changing either the magnitude or the direction of the ______ needed

Answer 2

force

Question 3

What type of simple machine is a flight of stairs?

Answer 3

inclined plane

Question 4

What type of simple machine is a wheel barrow?

Answer 4

complex machine: wheel/axle and lever

Question 5

What simple machine is used to cut things?

Answer 5

wedge

Question 6

If 320 J of work is done on a spring with a spring constant of 730 N/m, how far will it stretch?

Answer 6

PE = 1/2kx^2

x=.94

Question 7

How much work would be done on a spring (k=730 N/m) to stretch 1.5m?

Answer 7

PE = 1/2kx^2

x=810

Question 8

A grandfather clock keeps time with a pendulum. Which will be true of the clock if the pendulum is shortened?

Answer 8

The time intervals between each swing of the pendulum will decrease

Question 9

A pendulum clock is taken to the moon (g=1.6m/s^2). How long will the pendulum have to be in order for the clock to keep 1 sec?

Answer 9

l = 405 cm = 0.0405 m

Question 10

If the period of a certain wavelength (wavelength is = 4.5 m) is 2 seconds, what is the speed of the wave?

Answer 10

v=fλ
f=1/T t=period(s)

V = (4.5)(1/2)
V=2.25 m/s^2

Question 11

A factory whistle blows at a frequency of 1216 HZ. What pitch will the passengers of a car moving at 28 m/s away from the whistle hear if the speed of sound is 343 m/s.

Answer 11

(v+vd)
fd= fs ———
(v-vs)

fd=frequency received by detector
fs=frequency of wave emitted by source
vd=velocity of detector
vs=velocity of source
v=velocity of sound wave

           (343-28) fd= 1216   ———      =  116.73 Hz
            (343-0)

Question 12

A fire engine is moving south at 35 m/s while blowing its siren at a frequency of 400 Hz. What pitch will the passengers in a car that has already passed the fire engine hear if the car is traveling north at 18 m/s? Use 343 m/s for the speed of sound.

Answer 12

(v+vd)
fd= fs ———
(v-vs)

fd=frequency received by detector
fs=frequency of wave emitted by source
vd=velocity of detector
vs=velocity of source
v=velocity of sound wave

           (343-18) fd= 400   ———
           (343-35)

fd=422 Hz

Question 13

tuning fork

Answer 13

0.76 m at 13 degrees C

Question 14

which is increased when a single instrument string is tightened?

Answer 14

frequency of the standing waves