MOMENTUM 1
All bodies, which are in motion, have momentum. Momentum gives a measure of the Quantity of
Motion possessed by a body and is calculated as the product of mass, m, and velocity, v.
MOMENTUM = MASS x VELOCITY
or M = m× v Units Momentum = kg m s-1
Consider the following situations:
(i) a “small” mass moving at “high” velocity, say 5 kg at 50 m s-1, and
(ii) a “large” mass moving at “low” velocity, say 50 kg at 5 m s-1.
It can be seen that in each of these situations the momentum is the same (i.e. they both have the
same “quantity of motion”, namely 250 kg m s-1). This is the reason why a small ball bearing
moving at high speed shatters a sheet of glass just as easily as an housebrick moving at a much
lower speed.
EXAMPLE 1 – the upper die of a drop forging hammer has a mass of 50 kg and is allowed to fall
freely from a height of 2.5 metres onto a forging anvil. Determine the momentum of the upper die
at the instant it reaches the forging anvil.
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EXAMPLE 2 – a milling machine table and its component has a combined mass of 350 kg.
Determine the momentum of the table and component when traversing with a feedrate of
300 mm min-1.
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EXAMPLE 3 – if the momentum of a mass of 1 tonne is 13.333 x 103 kg m s-1 determine its velocity
in metres per second and kilometres per hour.
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1
, EXAMPLE 4 - a cable laying trolley having a mass of 300 kg moves with a constant velocity of
2 m s-1. At the start of the operation the cable drum, which is mounted on the trolley, has a mass of
950 kg. Determine the change in momentum of the trolley when 160 metres of cable have been
laid. The cable has a mass of 4 kg per metre.
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EXAMPLE 5 - a cleansing machine moving, moving with a speed of 9 km h -1, discharges 2 kg of
fluid per second onto the road surface. If the mass of the machine and fluid is initially 1000 kg,
determine the momentum after it has travelled a distance of 500 metres in a straight line.
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2
All bodies, which are in motion, have momentum. Momentum gives a measure of the Quantity of
Motion possessed by a body and is calculated as the product of mass, m, and velocity, v.
MOMENTUM = MASS x VELOCITY
or M = m× v Units Momentum = kg m s-1
Consider the following situations:
(i) a “small” mass moving at “high” velocity, say 5 kg at 50 m s-1, and
(ii) a “large” mass moving at “low” velocity, say 50 kg at 5 m s-1.
It can be seen that in each of these situations the momentum is the same (i.e. they both have the
same “quantity of motion”, namely 250 kg m s-1). This is the reason why a small ball bearing
moving at high speed shatters a sheet of glass just as easily as an housebrick moving at a much
lower speed.
EXAMPLE 1 – the upper die of a drop forging hammer has a mass of 50 kg and is allowed to fall
freely from a height of 2.5 metres onto a forging anvil. Determine the momentum of the upper die
at the instant it reaches the forging anvil.
…………………………………………………….. ……………………………………………………...
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…………………………………………………….. ……………………………………………………...
EXAMPLE 2 – a milling machine table and its component has a combined mass of 350 kg.
Determine the momentum of the table and component when traversing with a feedrate of
300 mm min-1.
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…………………………………………………….. ……………………………………………………...
…………………………………………………….. ……………………………………………………...
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EXAMPLE 3 – if the momentum of a mass of 1 tonne is 13.333 x 103 kg m s-1 determine its velocity
in metres per second and kilometres per hour.
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1
, EXAMPLE 4 - a cable laying trolley having a mass of 300 kg moves with a constant velocity of
2 m s-1. At the start of the operation the cable drum, which is mounted on the trolley, has a mass of
950 kg. Determine the change in momentum of the trolley when 160 metres of cable have been
laid. The cable has a mass of 4 kg per metre.
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EXAMPLE 5 - a cleansing machine moving, moving with a speed of 9 km h -1, discharges 2 kg of
fluid per second onto the road surface. If the mass of the machine and fluid is initially 1000 kg,
determine the momentum after it has travelled a distance of 500 metres in a straight line.
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