Hi I need help with my work can you help me please
I reckon it would be centimetres (cm).
In Burglar alarm, LDR acts an AND gate.
Answer: C
Explanation
The LDR is light dependent resistor. The principle used in the working of LDR is that the resistance is inversely proportional to the intensity of light falling on the diode.
In burglar alarm, LDR diode is combined with an IC 555.
Normally an LED source is made to be incident on the LDR diode with same intensity such that the resistance will be maintained constant.
As the LDR is connected with IC, the voltage will be high when light is falling on the diode.
The IC will give only two output states that is high and low. This confirms that LDR in burglar alarm act as AND gate.
As the thief enters and crosses the LED light, the intensity of the light falling on the diode will decrease leading to decrease in the voltage which will cause the alarm to beep.
Answer:
The average velocity is 2 m/s.
Explanation:
The velocity of the particle is the time derivative of its position 
![$v =\frac{dx(t)}{dt} = \frac{d}{dt}[t^2+2] $](https://tex.z-dn.net/?f=%24v%20%3D%5Cfrac%7Bdx%28t%29%7D%7Bdt%7D%20%3D%20%5Cfrac%7Bd%7D%7Bdt%7D%5Bt%5E2%2B2%5D%20%24)
Now the average from 
and 
is
Thus, the average velocity is 2 m/s.
