One at 0.90 m/s and the other at 1.90 m/s.

a) Assuming that they start at the same point and the same time, how much sooner does the faster student arrive at a destination 780 away?

b) How far would the students have to walk so that the faster student arrives 5.50 minutes before the slower student?

Please help!!

### 3 Answers

As you probably know, this is a Distance-Time-Rate question.

Consequently we must use the formula D = RT

In this question we must also watch our units of measurement

For student A, his Rate R = 0.9 and his Distance D = 780

His time T is given by T = D/R [from D=RT]

T = 780 / 0.9

T = 863.7 seconds…..[meters / meters /sec. = seconds]

For Student B, his rate is R=1.9, and Distance D also = 780

T = 780 ‘ 1.9 =410.5 seconds

The difference in time is 863.7 – 410.5 = 453.2 seconds

B arrives 453.2 seconds faster than A. That’s 453.2/60 = 7.55 minutes sooner

Part b)

We again use the D = RT formula

For the faster student, B, his Rate R remains 1.9

His Distance is “D”.

His time is t

Thus for B, D = 1.9t

For student A, Distance is also “D”

His rate R remains 0.9

His time is t + 5.5 minutes

Thus for A, D = 0.9(t + 5.5)

Now at this point it is usually wise to change the minutes to seconds. I shall do this, but as

you will see in a moment, it’s not necessary in this case to do this, because the factor 60

that we use to do this will cancel out in the final calculation.

Since both students travel the same distance eventually,

D of A = D of B

0.9(t+5.5) = 1.9(t)

0.9[(t+5.5)(60)] =1.9{t(60)]

There: t is in seconds but I’m going to cancel both sides by 60

0,9(t+5.5) = 1.9t

0.9t + 4.95 = 1.9t

4.95 = 1.9t-0.9t

4.95 = t

B should therefore walk 1.9 X t in seconds =1.9(4.95 X 60)….meters/sec X seconds = meters

= 564.3 meters

Cheers

For the first part, determine how long it takes each to travel the distance, and subtract the time.

I don’t know the 2nd part, sorry!!

I just posted a few Physics questions if you don’t mind taking a look!

1- first student need 14.44 minutes

2 2nd one need 6.84 minutes

3 they have to walk 2.36 m/s