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When to use law of momentum to find velocity rather than law of conservation of energy?
Wiki User
∙ 11y ago
While energy is ALWAYS conserved, this isn't always useful for calculations, since MECHANICAL ENERGY - the energy that can be easily calculated - is NOT always conserved. On the other hand, momentum is always conserved, whether a collision is elastic or inelastic. (In an elastic collision, energy is also conserved.) Thus, conservation of momentum is often more useful for calculations involving collisions.
Wiki User
∙ 11y ago
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Why two objects move in opposite direction one will have positive momentum and other negative momentum?
Quite simply, this means that momentum is a vector quantity; the direction is relevant. This is useful, for example, for calculations involving the conservation of momentum. Actually momentum is the product of velocity and mass, and velocity is also a vector quantity - thus, in this example, one object will have a positive velocity (more precisely: a positive component of the velocity along the x-axis, for example), the other, negative. Multiplying this velocity by the mass will also give a quantity which may be positive or negative (or rather, have positive or negative components).
A spaceship has a momentum of 20 000 kg-ms to the left and a mass of 500 kg What is the magnitude of its velocity?
momentum = mass x velocity, so velocity is momentum/mass. If the question asks for the magnitude then it's probably the absolute magnitude rather than a directional value (which would be negative as the space ship is heading to the left.
Which would have greater effect on kinetic energy of an object - doubling the mass or doubling the velocity?
Doubling mass affects kinetic energy in that the greater the mass, the greater the kinetic energy. OK, but if you have a 10kg mass traveling at 2m/s and it bumps into and sticks to a 10g mass, the resultant speed would be 1m/s. The momentum stays the same. KE before is 10*2*2/2= 20, while the KE after is 20*1*1/2= 10. So it is not that the above answer is wrong, but rather, you question is not clear.
Would you rather collide with someone walking running or standing still?
The energy involved is what causes harm; and that depends on the relative velocity.
Why does bouncing of an object result in a greater change of momentum rather than just colliding?
Momentum is the mass multiplied the change in velocity. If you think about it, bouncing an object means that it comes back from whatever it bounced against, giving it a negative velocity. This means that the change in velocity for bouncing is greater than for colliding because in an inelastic collision like the one described, the velocity goes to zero.
How is momentum used to determine collisions?
Momentum is traditionally used with Newtonian thinking in the conservation of energy, witness the desk toy with the 5 steel balls suspended by threads that cycle back and forth. Momentum here is based on simply equilibroum of the product of mass and velocity. On the Einstein relativity thinking, applicable to motions of objects approaching the speed of light, the laws of Newtonian logic fall apart, and one has to consider energy, mass and time. Here, momentum does not translate into velocity but rather distortions in time and mass.
Why two objects move in opposite direction one will have positive momentum and other negative momentum?
Quite simply, this means that momentum is a vector quantity; the direction is relevant. This is useful, for example, for calculations involving the conservation of momentum. Actually momentum is the product of velocity and mass, and velocity is also a vector quantity - thus, in this example, one object will have a positive velocity (more precisely: a positive component of the velocity along the x-axis, for example), the other, negative. Multiplying this velocity by the mass will also give a quantity which may be positive or negative (or rather, have positive or negative components).
What is consseveration?
Conservation has two definitions that I know of in this category. One is in scientific laws like conservation of angular momentum or conservation of energy. Conservation in this sense means that that element can't be created or destroyed. Conservation of energy, for example means that energy isn't created or destroyed, but rather it changes form (like from chemical energy to heat). The other conservation is like wildlife conservation which includes programs where people try to conserve the Earth's resources, wildlife, etc.
A spaceship has a momentum of 20 000 kg-ms to the left and a mass of 500 kg What is the magnitude of its velocity?
momentum = mass x velocity, so velocity is momentum/mass. If the question asks for the magnitude then it's probably the absolute magnitude rather than a directional value (which would be negative as the space ship is heading to the left.
Which would have greater effect on kinetic energy of an object - doubling the mass or doubling the velocity?
Doubling mass affects kinetic energy in that the greater the mass, the greater the kinetic energy. OK, but if you have a 10kg mass traveling at 2m/s and it bumps into and sticks to a 10g mass, the resultant speed would be 1m/s. The momentum stays the same. KE before is 10*2*2/2= 20, while the KE after is 20*1*1/2= 10. So it is not that the above answer is wrong, but rather, you question is not clear.
Would you rather collide with someone walking running or standing still?
The energy involved is what causes harm; and that depends on the relative velocity.
Why does bouncing of an object result in a greater change of momentum rather than just colliding?
Momentum is the mass multiplied the change in velocity. If you think about it, bouncing an object means that it comes back from whatever it bounced against, giving it a negative velocity. This means that the change in velocity for bouncing is greater than for colliding because in an inelastic collision like the one described, the velocity goes to zero.
Who promulgated the law of conservation of energy?
The law of conservation of energy was not invented, discovered, or promulgated by one single person. Rather, it gradually developed over time, as the understanding of energy improved, and more types of energy were understood to be interchangeable.
What effect does the mass of an object have on acceleration or deceleration of an object when an unbalanced force acts on it?
this is a tricky 1 because the mass itself does not affect it, but rather the friction of the plane it is moving on and the momentum (which does factor in mass) if no friction exists, then it is purely the momentum. momentum = mass x velocity
What is mommentum in science?
Momentum is a concept in physics that combines both the mass and velocity of an object. Basically it is the velocity of an object multiplied by its mass. Even though it relates very simply to the mass and velocity of an object it is still commonly used because it simplifies a great number of equations. Also some descriptions of reality are more convenient when using the mass and momentum rather than mass and velocity. This is especially true in particle physics where the simple relation illustrated above does not quite hold (a new factor is required, called the gamma factor) because the speeds approach those of light, and a momentum based model is more easy to work with.
Why does earth rotate constantly?
Actually it doesn't - but the changes are quite small. There is a physical law called Conservation of Angular Momentum - the total angular momentum (informally, we might say the "amount of rotation") can't increase or decrease in a closed system. If the distribution of masses on Earth changes, Earth's angular velocity can change - but any redistribution of masses is rather small-scale, compared to the size of the Earth. On the other hand, Earth rotates slower and slower over time - angular momentum is transferred to the Moon in this case.
If the speed of a moving object is doubled the kinetic energy of the object is?
The relation between kinetic energy is proportional to the square of velocity. Momentum is directly proportional to velocity. If the momentum of an object is doubled, but its mass does not increase (so velocity remains well below the speed of light), then its velocity is doubled. If the velocity is doubled then the kinetic energy increases by the square of 2, or four time.
