Q28 · 2022 · Paper 1Simple familiar7 marks
QUESTION 28 (7 marks)
An object of mass 200 g moves in a uniform circular path with a radius of 25 cm. The time taken for 10 revolutions is 3.0 s.
a)[2 marks]
Calculate the distance travelled by the object after 3.9 s. Show your working.
b)[5 marks]
Calculate the centripetal force acting on the object. Show your working.
WORKED SOLUTION
7 marksQCAA guide · typeset solution
ANSWER
See worked solution below.
Worked solution
l
d
u
is
i
tan
n
ce
2
0
number of revo t o
0
s
20.
3.9
2
.25
.
4
3
r
m
π
π
×
×
×
=
=
=
Distance travelled = 20 m (to two significant figures)
2
0.25
0.3
1
2
2
5. 36... m s
v
r
T
π
π ×
=
=
−
=
0.2
0.
.
2
2
2
5 2
5
21.93
36
mv
F
N
ne
r
t =
=
=
×
Centripetal force = 22 N (to two significant figures)
• recognises the scenario relates to the
circumference of circular motion [1 mark]
• calculates total distance travelled [1 mark]
• recognises the scenario relates to
velocity in circular motion [1 mark]
centripetal motion [1 mark]
• provides appropriate mathematical reasoning
[1 mark]
• demonstrates correct substitution [1 mark]
• calculates centripetal force of object [1 mark]
One QCAA sample method typeset for web; criterion wording is adapted from the official marking guide.
How many marks did you earn?
Compare your working with the guide above.