Vacum flask has inner layer of glass and outer body of plastic.the glass has a reflective metal layer..when a hot drink is poured into the flask it prevents conduction.tight lid stops the convection.when radiation tries to leave the hot drink the reflective layer of the glass reflects it back so no heat can escape.
Explanation:
F = 20N m= m1 a=10m/s²
m=m2 a=5m/s²
F = ma
<u>for the first one</u><u>:</u><u> </u>
f=m1 × a
20 = m1 ×10
20=10m1
m1=20/10
m1=2
<u>for</u><u> </u><u>the</u><u> </u><u>second</u><u> </u><u>one</u><u> </u><u>:</u>
f=m2×a
20=m2×5
m2= 20/5
m2= 4
since F=ma
F=(m1+m2) ×a
F =(4+2)×a
F =6×a
F=20(from the question above )
20=6×a
a=20/6
a=3.33
Answer:
The focal length of the lens should be -51.5 cm (a concave lens).
Explanation:
The purpose of the lens is to make objects at 48.5 cm appear at the healthy near point. The healthy near point is 25.0 cm.
We use the lens formula
where <em>f</em> = focal length, <em>u</em> = object distance and <em>v</em> = image distance.
In this case, <em>u</em> = 48.5 cm and <em>v</em> = -25.0 cm.
<em>v</em> is negative because the image is virtual an not real. (Here, we are using the real-is-positive sign convention)
The negative sign indicates the lens is concave.
Answer:
d
Explanation:
d because a b c are energy equation not work
Answer:
Explanation:
Let l be th length of pendulum
loss of height
= mg ( l - l cos50)
= mg l ( 1-cos50)
1/2 mv² = mgl ( 1-cos50)
v = √[2gl( 1- cos50)]
= √( 2 x 9.8 x .7 x ( 1-cos50)
= 2.2 m / s
speed at the bottom = 2.2 m /s
b )
centripetal acceleration
= v² / r
= 2.2 x 2.2 / .7
= 6.9 m /s²
C )
If T be the tension
T - mg = mv² / r
T = mg + mv² / r
= .13 X 9.8 + .13 X 6.9
= 2.17 N
