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A lead ball of mass 0.25 kg is swung round on the end of a string so that the ball moves in a
1
horizontal circle of radius 1.5 m. The ball travels at a constant speed of 8.6 m s–1.
(a) (i) Calculate the angle, in degrees, through which the string turns in 0.40 s.
angle ......................................... degree
(3)
(ii) Calculate the tension in the string.
You may assume that the string is horizontal.
tension ................................................. N
(2)
(b) The string will break when the tension exceeds 60 N.
Calculate the number of revolutions that the ball makes in one second when the tension is
60 N.
number of revolutions .....................................................
(2)
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(c) Discuss the motion of the ball in terms of the forces that act on it. In your answer you
should:
• explain how Newton’s three laws of motion apply to its motion in a circle
• explain why, in practice, the string will not be horizontal.
You may wish to draw a diagram to clarify your answer.
The quality of your written communication will be assessed in your answer.
(6)
(Total 13 marks)
A chemical centrifuge consists of two test-tube holders which can be spun round in a horizontal
2 circular path at very high speed as shown. The centrifuge runs at a steady speed of 3000
revolutions per minute and the test-tube holders are horizontal.
(a) Calculate the angular speed of the centrifuge in rad s–1.
........................................................................................................................
........................................................................................................................
(b) Calculate the magnitude of the acceleration at a point on the centrifuge 95 mm from the
axis of rotation.
........................................................................................................................
........................................................................................................................
(c) State the direction of the acceleration in part (ii).
........................................................................................................................
(Total 5 marks)
3
(3)
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A lead ball of mass 0.25 kg is swung round on the end of a string so that the ball moves in a
1
horizontal circle of radius 1.5 m. The ball travels at a constant speed of 8.6 m s–1.
(a) (i) Calculate the angle, in degrees, through which the string turns in 0.40 s.
angle ......................................... degree
(3)
(ii) Calculate the tension in the string.
You may assume that the string is horizontal.
tension ................................................. N
(2)
(b) The string will break when the tension exceeds 60 N.
Calculate the number of revolutions that the ball makes in one second when the tension is
60 N.
number of revolutions .....................................................
(2)
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, theonlinephysicstutor.com
(c) Discuss the motion of the ball in terms of the forces that act on it. In your answer you
should:
• explain how Newton’s three laws of motion apply to its motion in a circle
• explain why, in practice, the string will not be horizontal.
You may wish to draw a diagram to clarify your answer.
The quality of your written communication will be assessed in your answer.
(6)
(Total 13 marks)
A chemical centrifuge consists of two test-tube holders which can be spun round in a horizontal
2 circular path at very high speed as shown. The centrifuge runs at a steady speed of 3000
revolutions per minute and the test-tube holders are horizontal.
(a) Calculate the angular speed of the centrifuge in rad s–1.
........................................................................................................................
........................................................................................................................
(b) Calculate the magnitude of the acceleration at a point on the centrifuge 95 mm from the
axis of rotation.
........................................................................................................................
........................................................................................................................
(c) State the direction of the acceleration in part (ii).
........................................................................................................................
(Total 5 marks)
3
(3)
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Page 3 of 22
