An experiment to measure the speed of sound was carried out. David, who is 200m from a large brick wall clapped two pieces of wood together many times, each time he heard the echo (reflected sound) he immediately clapped again. Maryam used a stopwatch to time how long it took for 10 claps and echos. Explain why they timed 10 clap/echoes and not just 1?

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.

co2reflects heat radiation back to earth buning coal and oil emits co2 globe warms

hi there!

out of the two, (b) precision would be more reasonable.   however, both a and b could be pretty reasonable.

-awesomerepublic   : )

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.