can a body have constant velocty but a varying speed?give reasons.?
547930
Velocity is speed in a particular direction, anyone changes means the velocity is not constant.
399478
as long as mass is constant, the velocity of a body is constant. Newton's law.\n\nBut the word "conservation" does not mean constant. \n\nIf the velocity is transfered with out change, we can say it is conserved. This happens only in very few cases; elastic collision of equal masses.\n\nBut to cover that there is conservation of momentum.
399954
SPEED=dy/dt=distance/time.its not exactly something you invent.it was an axiom,a basis of understanding.
233087
this is where relativity comes into play. It depends from what viewpoint. speed is always relative to a "fixed" point (which might not be so "fixed" after all). get my drift?
686782
All right, I'll do my best. \n\nTwo rockets scenario: \n\nAssumptions: Both the rockets are out rigged with the same engines/propulsion systems, and have the same aerodynamic profile.\n\nThe ignition of the fuel generates a constant thrust, which translates into a constant upward force. How a force translates into motion of a body is dependent on the body's mass, more mass, slower the acceleration... less mass, more the acceleration. Thus, the heavier rocket will accelerate at a slower pace.\n\nDropping 2 bodies of different masses:\nAssumptions: Both have the same aerodynamic profiles.\n\nGravitation is not a constant force, but is a constant acceleration. Thus the rate of change of speed is fixed. The forces 'experienced' by the two masses are not the same, and the heavier one 'experiences' a larger force than the lighter one, in effect to balance out and make them drop at the same rate.\n\nKey equation (even though you didn't want one) is \nForce (F) = mass (m) x acceleration (a)\n\nIn the rocket scenario, Force is constant, so if mass goes up acceleration must go down, and vice-versa\n\nIn gravitation, Acceleration is constant, so more mass experiences a larger force.
55228
Not always. If the object is in motion, then no. The total energy, aka total mechanical energy is always constant due to the Law of Conservation and Energy. It depends on the problem. Certainly,if you know the total mechanical energy in the system than you can find a variable for the kinetic energy or gravitational potential energy,assuming you given other variables.
905757
This is uniform motion, if it is going in a straight line at constant speed.\n\nIf there are no forces acting upon a body, and therefore no acceleration (remember F=ma) or change in direction, nor any change in angular momentum, the motion is uniform. If it were changing direction, accelerating or going round in circles then it is non uniform.
28151
Acceleration due to gravity (NOT change in acceleration), which could also be described as change in velocity.  That's assuming no air resistance.  If there is air resistance, they will eventually reach terminal velocity after which their velocity will be constant, but this is not implied by "free fall," and given that the question sounds like it's from a basic middle school or high school physics class I'm guessing you're supposed to ignore air resistance.
641758
A better question is why do we feel ourselves moving on a lift or bus.\n\nOnly accelerations can be felt, not motion at a constant velocity. Einstein showed that motion at a constant velocity doesn't even have any meaning unless it is measured "relative" to some "stationary" observer, and even "stationary" has no meaning. But enough of that.\n\nEinstein also showed that acceleration is the same as gravity in that they can both be felt, and cannot be distinguished from each other unless you can look out a window. If you are in a closed box with no window, you cannot tell if you in a gravitational field or are accelerating.\n\nWhen a bus is traveling at a "constant" velocity, you in it are actually being accelerated in all different directions all the time as the bus bounces around. If the bus was traveling on a perfectly smooth surface at constant velocity, and had no windows, with no accelerations of any kind, you would not know you were moving.\n\nSame with the lift. You can feel only the accelerations up or down. If the lift is traveling perfectly smoothly at constant velocity with no accelerations, you would feel nothing, except that the pressure in your ears would tell you whether you are going up or down.
1108579
NO!!!\n\n\nThey dont fall with the same velocity, \n\nThere is a maximum /terminal velocity an object can attain while moving in a fluid. (in our case - air).\n\nAnother force acts on bullet in a direction opposite to that of g. \n\nThis force = 6 * pi * n * r * v \n\nr - radius of object,\nn - coeff of viscocity\nv - terminal velocity.\n\n\nThus the velocity with which the bullet will return to earth would be much less. (but still large enough )
903128
yes you would i beileve its neutons acceleration thing where it says something that weighs more has more interita therefore a elepant would have a tough time moving from side to side and would probably not catch you. its because its more diffucult to change its state of motion.
431787
Looks to be a subtle omission from the other posts about this.\n\nAcceleration is the rate of change of velocity with respect to time.\n\nThat is not insignificant. There can be relationships between numerous quantities in physics. One must specify which ones are dependet on the otehrs, otherwise a 'definition' is unclear and effectively useless.
66594
everyone else is pretty much right, it's just that everything in the universe is relative to an object's frame of reference. nothing is absolute. for example, you're on a bike moving at 10 m/s. you throw a baseball at 15 m/s relative to your frame of reference. to someone standing nearby, from their frame of reference the ball is moving at 25 m/s (the 15m/s you threw it at plus the velocity you're already moving.)  now, to a car moving slowly along the road at 25 m/s, the ball is not moving at all. it is stationary in the frame of reference of the car because they are moving at the same speed as each other. this is why it doesnt feel like you're moving backwards when you're in a car at a constant velocity(only when you speed up or slow down). also, if you drop a book in a moving vehicle, it will go straight down, not down and to the back.  that is because everything in the car is moving at the same speed, they're all in the same frame of reference. if you were to drop a  ball outside of the window of the car(assuming no air resistance) the ball would be moving at the same speed as the car and continue bouncing alongside the car(in reality it slows down substancially due to air resistance.) to you the ball would be stationary, aside from bouncing up and down, but to an outside observer, it would be moving forward.  it's all relative... that's the basic concept but there's also a lot more, more advanced applications involving the distortion of time as you reach near-light speed velocities... pretty interesting stuff.
716944
If there is no net force (i.e. sum of forces is zero) then there will be no change in velocity. So if the object was going 15 m/s and the net force is zero, then it will still be going 15 m/, (for 2 sec = 30 meters traveled). Same concept for your jet car - constant velocity means no net force ( there may be forces acting on it, but if the velocity is constant, they must sum to zero - net force is zero).\n\nAs Newton's first law says, "An object in motion tends to stay in motion unless acted on by an outside force." So constant velocity (i.e. stays in motion at the same velocity) means no net force acting on the object.
965485
You can do a theoretical top speed with physics, but it wouldn't account for the two main killers of speed which are aerodynamic drag and internal friction.  Without knowing those, you'd only be getting a false promise from your calculations.
1151411
Objects of different mass do fall at the same speed, but air resistance hinders this fact.  For example, if you drop a bowling ball and a feather at the same time on the Earth, obviously the bowling ball falls faster. \n\nHowever, on the moon, when the astronauts dropped a feather and a bowling ball, they hit the ground at the same time. \n\nIt would seem that the bowling ball should fall faster since gravity is pulling on it with more force. But, with the more mass, comes more inertia, which meas it resists being pulled more than the feather. So, the feather is pulled less, but it resists less as well, so because of that, they will fall at the same time. The relationship between the force of pull and the object's inertial compensates exactly so that all objects fall at the same rate.
697205
Yes, but to a smaller degree than when on the ground.\n\nThe inertia  and the weight of the wheel will have an effect as you change speed and gears.  This is not real "rolling resistance" but has a similar, but smaller effect.\n\nIf you are on a bike stand and rotate the pedals at 60rpm in the lowest (speed) gear, then change to the highest gear, you will see more   "resistance" until the wheel is at its new higher speed.  Then you will see some resistance to maintaining that speed and cadence.  This will be more than resistance in the lowest gear, and more pronounced the heavier the rear wheel.