A lightbulb is 3.8 m from a wall. What is the focal length of a lens that will form an image on the wall that is twice the size of the lightbulb? (focal length is f=0.84 meters)

What is the position (measured from the bulb) of the lens.

i don't understand. explain it clearly

the only real purpose of sputnik 1 was to beat the us into space. we were getting close to launching a useful satellite, explorer 1 - which launched on january 31, 1958. the ussr had to beat that, so they launched sputnik 1 on october 4, 19

when jerome paddle in flowing river towards east the net speed of jerome will increase

so the net speed of jerome will be given as

now the speed of paul will be same as it is given as he is running on the ground

so

so here we can say since the speed of jerome is more so he will win the race

now as we know the distance so the time difference is given as

so jerome will reach first and the time difference will be 203.55 s or 3.4 min