UPNG
Physics Division
1.10902 - Physics 1A External
ASSIGNMENT 2
th
DUE DATE: 10 of JUNE, 2019
Time: Before 4:06pm
(Total Score = 15+15+15+15=60marks)
Q1. Mr Moimoi is driving his car towards VC along the Waigani road. The radius of his car tyres
are 0.28 meters. Suddenly 60 meters in front of his car his angry wife stands still trying to stop
him. Moimoi decelerates at 7.0 m/s2 to avoid hitting his dear wife. The wheels initial angular
velocity before deceleration was 100.0 rad/s. Calculate the following quantities:
a)
Calculate the angular acceleration () of the tyres of Moimoi’s car assuming they do not
slip on the pavement.
(3 marks)
b)
Calculate the number of revolutions the tyres make before coming to a rest. (3 marks)
c)
Calculate the amount of time it takes the car to stop completely.
d)
Calculate the distance travelled during the time calculated in part (c) above. (2 marks)
(3 marks)
Q2. Buoys are often used in a mooring system for boats to be moored (used to park boats on
water).The mooring-buoy consists of a sphere which is held below the surface of the sea by a
galvanized chain anchored to the bottom of the sea. The sphere has a volume of 2.5m 3 and the
tension in the chain is 3500N.
(a)
Calculate the buoyant force exerted by the water on the sphere. Assuming the sphere is
just below the surface of the sea and the pole is sticking out of the water. (5 Marks)
(b)
What is the mass of the sphere?
(c)
The chain breaks due to over exposure to salt from the sea water and the sphere rises to
the surface. When the sphere comes to rest, what fraction of its volume will be
submerged?
(5 Marks)
(5 Marks)
Q3. One end of a horizontal string of linear mass density 6.6 x 10-4 kg/m is attached to a small
amplitude mechanical 120 Hz oscillator. The string passes over a pulley, a distance 1.50m away
and weights are hung on the end, as shown in the figure below. What mass must be hung from
the end of the string to produce a standing wave with one “loop”?
(5 Marks)
b) A sinusoidal wave on a string travelling in the – 𝑥 direction has an amplitude of 1.00cm,
wavelength 3.00cm and frequency 245 Hz. At 𝑡 = 0, the particle of string at 𝑥 = 0 is
displaced by a distance 𝐷 (0, 0) = 0.80 𝑐𝑚 above the origin and is moving upward.
Determine the function of 𝑥 and 𝑡 that describes this wave.
(5 Marks)
c) An earthquake P-wave travelling 8.0 km/s strikes a boundary within the earth between
two kinds of material. If it approaches the boundary at an incident angle of 52º and the
angle of refraction is 31º, what is the speed in the second medium?
(5 Marks)
Q4. A box of mass M = 10,000 grams rests on a 35° inclined plane with the horizontal. A string
is used to keep the box in equilibrium. The string makes an angle of 25 ° with the inclined plane.
The coefficient of static friction between the box and the inclined plane is 0.3.
a)
Draw a Free Body Diagram including all forces acting on the particle with their labels.
b)
Find the magnitude of the Tension, T, in the string.
(8marks)
c)
Find the magnitude of the Friction Force acting on the particle.
(4 marks)
(3 marks)