for science people?

Question

Which of the following cars is accelerating?
a fast moving car
a slow moving car
a car that is slowing down
a car that is not moving


Nancy is training for a marathon. She jogs 10 miles straight south of her home each morning. It takes her 80 minutes. Assuming she runs at constant speed, what is Nancy’s velocity?
0.125 miles/minute
1.25 miles/minute
12.5 miles/minute
8 miles/minute


Who can rollerblade faster—Jenny, who can go 50 m in 30 s, or Jack, who can go 60 m in 40 s?
Jenny
Jack
They travel at the same speed.
It is impossible to tell with the information provided.

Answer 1

accelerating means the speed is changing. this can be from slow to fast or fast to slow.
The car slowing down is accelerating at a negative rate (decelerating)

Notice all the answers are miles/minute. This is a clue that you have to divide miles by minutes. 10 miles divided by 80 minutes is .125 miles/minute

Again speed is always found by dividing by the time.
Jenny 50/30 = 1.67
Jack 60/40 = 1.5
So Jenny is faster.
[if you have to guess, pick the girl. these problems are always written by people trying to be p.c.]

Answer 2

Question 1:

The only car which is "accelerating" (ie. changing
velocity) is "a car that is slowing down". All
of the other cars are maintaining a constant
velocity (and thus are not accelerating.


Question 2:
Nancy jogs 10miles/80mintes = 0.125 miles/minute
[Just do the division]

Question 3:

50m/30s = 1.67 m/s
60m/40s = 1.50 m/s

Thus, Jenny rollerblades faster than Jack.

Answer 3

The acceleration is the rate at which the speed is changing.
(change is the key)

The velocity is speed AND direction. A correct answer would be equivalent to:
1 mi in 8 minutes towards the South

(South should be part of the answer if "velocity" is called for). I suspect that it is used as a synonym for "speed" in this case (unless you omitted the word South from the answers)

Compare 50/30 and 60/40. Do the division (to find speed in m/s) if you have to. One number will be greater than the other.

Answer 4

The car that is slowing down, but its accelerating backwards. :)

1.25 miles/min

Jenny is going 1.666 repeating meters per second.

Jack is only going 1.5 meters per second.

Jenny is faster.