35. The following graph describes the motion of a girl who travels to meet her friend
who stays 500 m from her house.
5 marks)
G
500
C
D
400
300
Displacement
A
200
В
100
0
2 4 6 8 10 12 14 16
Time since leaving the house (min)
a) How much time did she take to reach her friend's house?
b) What distance did she travel in the first 12 minutes?
c) During which time intervals was she moving towards her own house?
d) For how many minutes was she at rest during her entire journey?
e) Calculate the velocity by which she returned home.
Answers
Answer:
a)14min
b)600m
c)from 14 to16 minutes
d)for 6 minutes
e)4.16m/s
Explanation:
a)the displacement is given starting from this girl's house,so after 14 minutes she have reached her friend's house,in the remaining two minutes she had returned to her house,so those two minutes won't count as time took by her to reach her friend's house.
b)in the chart they've given the displacement,not the distance, distance and displacement are different from each other because displacement is a vector which has a direction and a magnitude,while distance is not a vector, it only has a magnitude, doesn't have a direction.so you have to count the distance DE also to find out the answer.
c)between 14 and 16 minutes the displacement has dropped from 500m to 0,which means she had returned to the starting point where the motion started,and that's her house..
d)in the following parts of the motion,her displacement hadn't changed,which means she was at rest at that time,those parts are,
AB,CD,EF
the relevant time period belonging to those parts are,2mins for each,so she was at rest for 6 minutes.
e)velocity=displacement/time
=500m/120s
(in this part,2 mins=2×60 seconds)
=4.16m/s
Answer:
(a) 14mjns
(b) 600m
(c) 14 to 16 mins
(d) 6mins
(e) 4.16m/s