Answer:
To unlock a door and indicate to the person that the door is now unlocked
Explanation:
Schools all have doors locked. Visitors/parents need to press a button. That creates a buzz sound in the office, secretary presses a button to unlock the door. The person trying to enter the school hears a buzz and the secretary telling them to enter the building.
Answer:
Vr = 3.24m/s
The boat is going 3.24m/s relative to the bank of the river.
Explanation:
The relative speed of the boat to the bank Vr is the resultant of speed of boat relative to the water Vb and the speed of boat as a result of the water current or wind Vw
Vr = √(Vb^2 + Vw^2) .....1
Given;
Vb = 2.6m/s
Vw = distance downstream/time = 690m/355s
Vw = 1.94m/s
From equation 1 above; substituting the values
Vr = √(2.6^2 + 1.94^2)
Vr = 3.24m/s
The boat is going 3.24m/s relative to the bank of the river.
110 grams
mass of salt + mass of water
10 + 100
110g
Answer:
Heat energy does not cool. Objects cool. Energy is not an object. Now, what happens when an object cools is that it gives off some of its thermal energy by one or more mechanisms: radiation, conduction, or convection. In radiation the energy escaped the object as electromagnetic waves - you see the red hot poker slowly dim as it cools, in conduction the energy is transferred Mechanically by the atoms of the hot object being in physical contact with those of the cool object and in convection the hot material moves to a cooler region where it gives up its heat energy by either radiation or conduction.
Answer:
Ф = 239.73 rad
Explanation:
α = 12 + 15×t
W = ∫α×dt
= ∫(12 + 5×t)×dt
= 12×t + 2.5×t^2
then:
Ф = ∫W×dt
= ∫(12×t + 2.5×t^2)dt
= 6×t^2 + 5/6×t^3
therefore the angle at t = 4.88s is:
Ф = 6×(4.88)^2 + 5/6×(4.88)^3
= 239.73 rad
