I calculated it to be ~58357J (whole number) since m = 420kg and v=60/3.6 = 16.67m/s
k.e. = (1/2)mv² = (1/2)*420*(16.67)² = 58357J
but the answer says 3500J which means I am completely off. what am i doing wrong here?
k.e. = (1/2)mv² = (1/2)*420*(16.67)² = 58357J
but the answer says 3500J which means I am completely off. what am i doing wrong here?
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I have checked the calculations and guess what, your answer (58357J) is actually right.
You haven't done anything wrong ; Infact it is the answer which is given wrongly.
They have forgotten to square the velocity while calculating the Kinetic energy.(that's the mistake in THEIR answer)
(1/2)*420*(16.67) = 3500.7J
So no need to worry :-)
You haven't done anything wrong ; Infact it is the answer which is given wrongly.
They have forgotten to square the velocity while calculating the Kinetic energy.(that's the mistake in THEIR answer)
(1/2)*420*(16.67) = 3500.7J
So no need to worry :-)
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Maybe its the book that you are using
Kinetic energy of rigid bodies
In classical mechanics, the kinetic energy of a point object (an object so small that its mass can be assumed to exist at one point), or a non-rotating rigid body, is given by the equation
where m is the mass and v is the speed (or the velocity) of the body. In SI units (used for most modern scientific work), mass is measured in kilograms, speed in metres per second, and the resulting kinetic energy is in joules.
For example, one would calculate the kinetic energy of an 80 kg mass (about 180 lbs) traveling at 18 metres per second (about 40 mph, or 65 km/h) as
Ek = (1/2) · 80 · 182 J = 12.96 kJ
Since the kinetic energy increases with the square of the speed, an object doubling its speed has four times as much kinetic energy. For example, a car traveling twice as fast as another requires four times as much distance to stop, assuming a constant braking force.
The kinetic energy of an object is related to its momentum by the equation:
where:
is momentum
is mass of the body
For the translational kinetic energy, that is the kinetic energy associated with rectilinear motion, of a body with constant mass , whose center of mass is moving in a straight line with speed , as seen above is equal to
where:
Kinetic energy of rigid bodies
In classical mechanics, the kinetic energy of a point object (an object so small that its mass can be assumed to exist at one point), or a non-rotating rigid body, is given by the equation
where m is the mass and v is the speed (or the velocity) of the body. In SI units (used for most modern scientific work), mass is measured in kilograms, speed in metres per second, and the resulting kinetic energy is in joules.
For example, one would calculate the kinetic energy of an 80 kg mass (about 180 lbs) traveling at 18 metres per second (about 40 mph, or 65 km/h) as
Ek = (1/2) · 80 · 182 J = 12.96 kJ
Since the kinetic energy increases with the square of the speed, an object doubling its speed has four times as much kinetic energy. For example, a car traveling twice as fast as another requires four times as much distance to stop, assuming a constant braking force.
The kinetic energy of an object is related to its momentum by the equation:
where:
is momentum
is mass of the body
For the translational kinetic energy, that is the kinetic energy associated with rectilinear motion, of a body with constant mass , whose center of mass is moving in a straight line with speed , as seen above is equal to
where:
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