UNIT 4 : MOMENTUM
Q1
A DVD is rotating at 570 rotations per minute.
What is its angular velocity in radians per second?
(1)
A 1.5
B 10
C 60
D 3600
(Total for question = 1 mark)
Q2.
A student read the following extract from a textbook.
'In an elastic collision between objects of equal mass, where one is initially stationary, the objects move off at 90° to each
other after the collision.'
The student investigated this using a collision between two identical steel balls, each of mass 66 g.
(a) The diagrams illustrate the collision between the balls.
1
, In one experiment u1 was 0.72 m s−1 and θ was 29°. For such a collision it can be shown that, if the balls are to
separate at 90°, then
v1=0.63ms−1
φ= 61°
v2=0.35ms−1
(i) Show that these values satisfy the conditions for conservation of momentum in the initial direction of ball 1.
(4)
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(ii) Show that these values satisfy the condition for elastic collisions.
(3)
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2
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(b) The photograph shows the student's actual results for this experiment. The positions of the colliding balls at successive
time intervals have been overlaid on a single image.
(i) State the additional information that the student needs in order to determine the speeds of the balls.
(2)
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(ii) The student looked at the photograph and noticed that the angle between the paths of the two balls after
thecollision was not 90°. He modelled the collision on a computer.
He used the same initial conditions for ball 1 and the same value of θ. The computer calculated the total kinetic energy
after the collision for a range of angles φ. The following graph was produced.
3
Q1
A DVD is rotating at 570 rotations per minute.
What is its angular velocity in radians per second?
(1)
A 1.5
B 10
C 60
D 3600
(Total for question = 1 mark)
Q2.
A student read the following extract from a textbook.
'In an elastic collision between objects of equal mass, where one is initially stationary, the objects move off at 90° to each
other after the collision.'
The student investigated this using a collision between two identical steel balls, each of mass 66 g.
(a) The diagrams illustrate the collision between the balls.
1
, In one experiment u1 was 0.72 m s−1 and θ was 29°. For such a collision it can be shown that, if the balls are to
separate at 90°, then
v1=0.63ms−1
φ= 61°
v2=0.35ms−1
(i) Show that these values satisfy the conditions for conservation of momentum in the initial direction of ball 1.
(4)
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
(ii) Show that these values satisfy the condition for elastic collisions.
(3)
.............................................................................................................................................
2
, .............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
(b) The photograph shows the student's actual results for this experiment. The positions of the colliding balls at successive
time intervals have been overlaid on a single image.
(i) State the additional information that the student needs in order to determine the speeds of the balls.
(2)
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
(ii) The student looked at the photograph and noticed that the angle between the paths of the two balls after
thecollision was not 90°. He modelled the collision on a computer.
He used the same initial conditions for ball 1 and the same value of θ. The computer calculated the total kinetic energy
after the collision for a range of angles φ. The following graph was produced.
3
