TUTORIAL 3B-PHYSICS, SHF 1215, SEM 2, 2010/2011
Chapter: Circular Motion
1 A bicycle being repaired is turned upside down, and one wheel of 33 cm in diameter is rotated at a rate of 6.28 rad/s. The wheel slows uniformly until it stops in 15 s.
(i) How many revolutions does it make during this time?
(ii) How far will a point on the edge of the wheel have traveled in this time?
2 A floppy disc in a computer rotates from rest up to an angular speed of 31.4 rad/s in a time of 0.892 s.
a) What is the angular acceleration of the disk, assuming the angular acceleration is uniform.
b) How many rotations does the disk make while coming up to speed?
c) If the radius of the disk is 4.45cm, find the final linear speed of a microbe riding on the rim of the disk.
d) What is the magnitude of the tangential acceleration of the microbe at this time?
3 A 3 500 kg aeroplane is flying in a circular path of radius 2 000 m at a constant speed of 40 ms-1.
(i) On the diagram above, use a labelled arrow to show the direction of tangential velocity, centripetal acceleration and centripetal force acting on the aeroplane.
(ii) How long will it take the aeroplane to fly one complete circle?
(iii) What is the magnitude and direction of the acceleration of the aeroplane?
4 The wheel of a moving car slows uniformly from 60.0 rads-1 to 120.0 rads-1 in 4.0s. The radius of the wheel is 0.35m. Calculate
(a) the angular acceleration of the wheel.
(b) the tangential acceleration of the wheel.
(c) the total acceleration of the wheel at 4.0 s
5 Discus throwers throw the discus by twisting the motion of their bodies as shown. Starting from rest, the thrower accelerates the discus to a final angular speed of 15 rad/s in a time of 0.270s before releasing it. During the acceleration, the thrower moves the discus in a circular arc of radius 0.810m.
[b] Calculate the angular displacement of the discus.
[c] Calculate the tangential acceleration of the discus.
[d] If the mass of the discus is 2.0kg, calculate the centripetal force exerted by the thrower at the point of release
6 A child on a merry-go-round is moving with a speed of 1.35 m/s when 1.20 m from the center of the merry-go-round. Calculate (a) the centripetal acceleration of the child, and (b) the net horizontal force exerted on the child whose mass is 25.0 kg. (c) What happens to the speed when the child moves towards the center of the merry-go round assuming that the period of revolution remains the same?
7 A 0.40 kg ball attached to the end of a horizontal cord, is rotated in a circle of radius 1.3 m on a frictionless horizontal surface. If the cord will break when the tension exceeds 60 N, what is the maximum speed the ball can have?
8 In a tumble drier, clothes are placed inside a drum with small holes in it. The drum rotates at high speed and water escapes through the holes. A particular drum has a radius of 0.25m and rotates at 900 revolutions per minute.
(i) Calculate the speed of the rim of the drum.
(ii) Calculate the force necessary to allow a piece of clothing of mass 0.4kg to perform circular motion.
No comments:
Post a Comment