Sally walks to the store at a rate of 3 m/s for 15 seconds. She stops at a crosswalk for 4 seconds until the sign tells her she can go. Sally ran across the street at 5 m/s for 3 seconds until she reached the other side. She then walked the rest of the way to the store at 3 m/s. If the store was 100 m away from where Sally started originally and it took her 250 seconds to get there, what was her average speed?

Average speed= 0.4 m/s  

Explanation:

step one:

simply put average speed is defined as the total distance travelled divided by the total time taken.

step two:

given data

total distance is the distance from where she started to the store

which is 100 m

also, we are told that the total time taken is 250 seconds

step three:

Hence we can compute the average speed as

average speed= 100/250

average speed= 0.4 m/s  

Answerthe energy required is 1.60 × 10⁻¹⁸ j, to three significant figures.explanationwe define electric potential as the ratio electric potential energy to the charge,    then the following gives us the potential difference,      the formula  may be on your formula sheet.the change in electric potential energy would be the energy that would needed to move it from point a to point b. solving for that, we get    using q = 8.00  × 10⁻¹⁹ c and  δv = 2.00 v, we get    the energy required is 1.60 × 10⁻¹⁸ j, to three significant figures.