Example of a body having zero velocity but still has acceleration.?

Question

explain why?

Answer 1

If you are at rest, you will have zero speed which will give you zero velocity with respect to the Earth; however gravity is still acting on you which is an acceleration. The reason you don't move is because you have another force (the normal force) countering your weight, which gives you a net acceleration of zero.

Answer 2

A car that is traveling around a rotonda, that is it started from a certain point in the rotonda, moved around the rotonda and returned to that point, is an example of a body having zero velocity yet stil has acceleratrion.
Velocity is a vector quantity. That means it both includes magnitude and direction. "400 mph" is an example of magnitude and it means it is not a vector. But if we say "400 mph east", it is an example of velocity and is a vector quantity.
Velocity is defined as the ratio of displacement and time. Note that displacement is different from distance . Distance is usually larger than displacement. Displacement is characterized by how far that a body had traveled from a reference point through a straight line while distance disregard this straight line.
So in the case above the car have acceleration but the velocity can be zero. Wether the car changes it speed during intervals of time or not, it always have acceleration. Remember that the displacement of the car in the rotonda will be zero because it returned to its starting (reference) point. From the formula of velocity of that v(velocity)=d(displacement)/time, we can calculate the velocity of the car by giving an arbitrary value for the time and its displacement. Shall we say its time elapsed is 20 seconds and the displacement is 0 m. Then the velocity is 0 m/20 sec or 0 m/sec or 0.

Answer 3

There are two good examples. Velocity is a vector representing motion in a specific direction (down, up or north, etc.). Speed is motion in any direction. Acceleration (also a vector) is a change in velocity in a specific direction. Therefore, if you drop a rock under the influence of earth's gravity, at the instant of release it will have zero velocity but an acceleration, g, due to gravity.

If a car is driving at a constant speed in a perfect circle, the direction of its maximum velocity is always changing and it is therefore constantly accelerating. At one instant it may be traveling due east while its velocity in a northerly direction is instantaneously zero.

Answer 4

Closest thing? Astronaut in space, which appears to have zero velocity relative to the spacecraft they are on. Yet, they are falling toward earth constantly as they orbit around the planet.

The truest sense of zero velocity you are talking about only appears momentarily, when the constant acceleration is acting directly against the initial velocity of the object. At certain moment in time, the velocity of the object will be zero. Examples could be objects moving against gravity without escaping the gravitational pull, pendulum swings, and mass on a spring, etc.


XR

Answer 5

All bodies which are at rest are set into motion only when there is acceleration.

Initially its speed is zero; but in the next instant it acquires a speed because of a force in other words because of acceleration.

Unless there is change in speed, it cannot start from rest; i.e. unless there is acceleration it cannot move.

All bodies which execute simple harmonic motion, like simple pendulum are brought to rest at a point where the acceleration is maximum. If there is no acceleration it cannot change its speed from zero.

Bodies thrown up come to rest at a certain height; its speed begins to increase in the down ward direction from zero because of acceleration. If there is no acceleration it cannot change its speed from zero.

When you hit a ball to the ground it is momentarily brought to rest; because of acceleration it rebounds.

Thus when ever a net force acts on a body there is acceleration and it is immaterial whether it was at rest or not; but there will definitely be a change in velocity i.e. acceleration.

Answer 6

Acceleration is a=dv/dt. if at a certain moment the velocity is 0, but at the next moment it varies, the acceleration is not zero, but positive for an increase in velocity and negative for a decrease in velocity. If you throw an object in the air, at its highest altitude it has zero velocity, but acceleration g.

Answer 7

If you throw a ball up, on the maximum height v is instantaneously 0, but a is not zero because at that point ball changes direction and a is pointing down - remember, a is change in either the magnitude or direction of the velocity.

Answer 8

throw a ball directly up in the air - it will be constantly subject to the accel due to gravity, however at teh turning point (highest point in journey) it will have a velocity (relative to Earth position) of zero.

may help to think of a speed(velocity)-time graph. for this motion you would get a straight line from a +ve velocity through to a -ve velocity. the line would have an approx steady gradient - this is accel, but would pass through a point of v=0 m/s

Answer 9

A projectile travelling directly up has downward acceleration of 9.8 m/s2 all the time, even at the top when it is, for an instant, stopped.
Similarly for a pendulum at the outsides of its swings, although the acceleration is less than "g".

Answer 10

An example would be yourself, fast asleep.
The reason is that your body is subjected to the Earth's gravitational pull, which is a form of acceleration of 9.8metres per second squared.