I'm lost about acceleration... =[?

Question

1) What is the acceleration of a car moving along a straight-line path that increases its speed from zero to 100km/h in 10 seconds?

2) By how much does the speed of a verhicle moving in a straight line change each second when it is accelerating at 2km/h x seconds? at 4 km/h x seconds? At 10 km/h x seconds?

3) Why does the unity of time enter twice in the unit of acceleration?

Answer 1

1) The thing to remember is that velocity (or speed) is a rate of change of distance over time.  Acceleration is the change in velocity over time. So, if v0=0 km/h and v1=100km/h, then the change over time is:

(v1-v0)/time.  

However, don't forget to convert the time in seconds to hours, since hours is in the units of velocity.  Hope this helps!

Answer 2

ok i am answering the last one..i am not feeling well enough to read problems..

acceleration is rate of change of valocity with time

rate of change of velocity=difference in velocity in two times...velocity has time in its unit.. m/s

now rate of change of velocity(=m/s) with time(s)...

by simple algebra its m/(s*s)

Answer 3

all i know is that at number one you divide O.o

Answer 4

acceleration is the change in velocity over time.

so for part a) the velocity changes from 0 to 100 km/h. a = vf - vi/t

vf = final velocity

vi = initial velocity

t = time

(100 km/h - 0 km/h)/10 sec  = 10 km/hr/sec

b) if it is accelerating at 2km/h/sec, then its speed is changing 2 km/h each second .... repeat for the other parts

c) time enters twice because speed is distance per unit of time and acceleration is change in speed per unit of time.