HORIZONTAL CIRCULAR MOTION
TEST 2
Q1)
A boy of mass 25.0 kg stands on a rotating platform which rotates
6.00 times per minute. Radius of his circle is 2.50 m.
a)
What is the frequency of rotation in Hertz?
(1 Hz = 1 revolution per second)
b)
What is the period of rotation in seconds?
c)
Determine the acceleration of the boy, if radius of the circular path of the boy is 2.50 m.
[0.987 m s-2; towards the centre]
d)
What is the net force acting on the boy?
e)
What does provide the net force?
f)
What will be the effect on the speed if the boy moves further away from the central shaft (i.e. his
radius is increased)? Circle the correct answer and give reason.
(i) speed will not change
[0.100 Hz]
[10.0 s]
[ 24.7 N; towards the centre]
(ii) speed will decrease
(iii) speed will increase
Reason:
Dr Akilan PhD UWA
©Advanced Science Academy
AdScAc@gmail.com
M: 0418 887 707
[1]
HORIZONTAL CIRCULAR MOTION
TEST 2
Q2)
A year 12 student is swinging a 200 g rubber stopper in a
horizontal circle of radius 85.0 cm. When the speed of the
stopper reaches 7.10 m s−1 the string breaks.
a)
What is the magnitude and direction of the
centripetal force when the string brakes?
[11.9 N; towards the centre]
b)
What is the angle of the string to the horizontal when it brakes?
[9.350]
c)
What is the magnitude of tension in the string when it brakes?
[12.1 N]
d)
A fellow student caught the rubber stopper before landing. Determine the horizontal distance the
stopper travelled if the net vertical displacement during the flight is 0.650 m (Assume air resistance
is negligible).
[Hint: Draw a diagram]
[2.58 m]
Dr Akilan PhD UWA
©Advanced Science Academy
AdScAc@gmail.com
M: 0418 887 707
[2]
HORIZONTAL CIRCULAR MOTION
TEST 2
Q3)
Engineers when designing rods bank the circular section of the roads.
a)
Draw a force vector diagram to show
the net force.
Vector diagram
b)
c)
Describe the purpose of banking curved roads.
Determine the maximum speed a vehicle can travel on a winter day when the road is covered with
thin layer of ice. The banking angle of the road = 15.50 and the radius of the bend = 40 m.
[10.4 m s-1]
Dr Akilan PhD UWA
©Advanced Science Academy
AdScAc@gmail.com
M: 0418 887 707
[3]
HORIZONTAL CIRCULAR MOTION
TEST 2
Q4)
The diagram shows an athlete of mass 70.0 kg is leaning towards the centre of the circular bend whilst
skating around a circular bend.
a)
What is the purpose of leaning?
b)
Determine the leaning angle to have a speed of 12.0 m s-1 on a circular bend of radius 20.0 m.
[36.30; to the vertical]
c)
What is the magnitude of the centripetal force acting on the athlete?
Dr Akilan PhD UWA
©Advanced Science Academy
AdScAc@gmail.com
[504 N]
M: 0418 887 707
[4]
HORIZONTAL CIRCULAR MOTION
TEST 2
Q5)
Jason is about to pick his 12.0 kg travelling
bag (labelled as J) off the belt conveyor in
the Cebu airport.
The conveyor belt is moving at a constant
speed of 4.75 m s-1 and has a radius of
curvature of 12.0 m.
a)
What is the magnitude of the centripetal acceleration of bag J?
b)
Show the direction of acceleration of bag J in the above diagram?
c)
Explain why the bag J is accelerating even though the speed is constant?
[1.88 m s-2]
Although speed is constant, the velocity is changing because the direction is changing. This
change in direction is caused by the presence of an unbalanced force towards the centre of circle
and results in an acceleration due to change in velocity (a = v/t or v2/r).
d)
Determine the centripetal force experienced by bag J.
[22.6 N; towards the centre of circle]
e)
Explain why bag J is not slipping?
Frictional force between the bag and the conveyor belt prevents the bag slipping from the belt.
Dr Akilan PhD UWA
©Advanced Science Academy
AdScAc@gmail.com
M: 0418 887 707
[5]
HORIZONTAL CIRCULAR MOTION
TEST 2
Q6)
A car is being driven in a banked road on a rainy day when the friction between the road and tyre is
negligible.
Determine the safest speed limit of the car to negotiate the bend without skidding, if the radius of circular
bend is 20.7 m.
[9.73 m s-1]
Q7)
Determine the banking angle (θ) of the curved road of radius 30.0 m so that the vehicles travelling up to
48.0 km h-1 will not slide on a rainy day when there is negligible friction between the road and tyres.
[31.20]
Dr Akilan PhD UWA
©Advanced Science Academy
AdScAc@gmail.com
M: 0418 887 707
[6]
HORIZONTAL CIRCULAR MOTION
TEST 2
Q8)
Fernandez rotates 2.00 kg discus along a circular path of radius 0.900 m at a constant speed of 18.0 m s-1.
a.
Is the discus accelerating? Circle the correct answer.
i)
Yes
ii)
No
b.
Explain the reason, if your answer to part (a) is no.
c.
Explain the reason if your answer to part (a) is yes.
d.
Determine the acceleration, if your answer to part (a) is yes.
[360 m s-2; towards the centre of circle]
e.
Show by calculation that the time taken for one complete rotation is 0.314 second.
f.
Calculate the frequency of rotation.
[Hint: f = 1 ]
[3.18 Hz]
T
Dr Akilan PhD UWA
©Advanced Science Academy
AdScAc@gmail.com
M: 0418 887 707
[7]
HORIZONTAL CIRCULAR MOTION
TEST 2
Q9) HIGH ACHIEVERS
A metal ball of mass 5.00 kg is attached to a high tensile string of unknown length and rotated horizontally
with a constant velocity of 10 m s-1. The frequency of the rotation is 27.0 revolution per minute.
Calculate the length of the string.

 Hint: f = 27 Hz;
60

Dr Akilan PhD UWA
[3.75 m]

T = 1; v = 2πr; tan θ = v 
f
rg 
T
2
©Advanced Science Academy
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M: 0418 887 707
[8]