Answer:
50
Explanation:
The mechanical advantage of a machine is given by

where
is the output force
is the input force
For the crowbar in this problem,
is the force in input applied by the worker
is the force that the machine must apply in output to overcome the resistance of the window and to open it
Substituting into the equation, we find

If the lightbulb A in the circuit shown in the image burned out, the path for the current to flow is disrupted because one of its terminals is connected direct to the source. So, there will be no current through the lightbulbs B, C, and D, and they will turn off. Similarly it will happen, if the lightbulb D burned out.
If the lightbulb B burned out the current will continue circulating through the lightbulbs A, C, and D, because lightbulb B is connected in parallel. Similarly it will happen, if the lightbulb C burned out.
Answer:
The kinetic energy of the cell phone is 9J
Explanation:
The kinetic energy is the energy possessed by a body by virtue of motion.
The kinetic energy is expressed as
KE= 1/2m(v)²
Given data
Mass of cell phone m= 80g--to kg=80/1000= 0.08kg
Velocity of cell phone v= 15m/s
Substituting our given data we have
KE= 1/2*0.08(15)²
KE= (0.08*225)/2
KE=18/2
KE= 9J
Convex mirrors only produce virtual images