# What is Change in velocity: Definition and 46 Discussions

Delta-v (more known as "change in velocity"), symbolized as ∆v and pronounced delta-vee, as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as launching from or landing on a planet or moon, or an in-space orbital maneuver. It is a scalar that has the units of speed. As used in this context, it is not the same as the physical change in velocity of the vehicle.
As a simple example, take a conventional rocket-propelled spacecraft which achieves thrust by burning fuel. The spacecraft's delta-v is the change in velocity that spacecraft can achieve by burning its entire fuel load.
Delta-v is produced by reaction engines, such as rocket engines, and is proportional to the thrust per unit mass and the burn time. It is used to determine the mass of propellant required for the given maneuver through the Tsiolkovsky rocket equation.
For multiple maneuvers, delta-v sums linearly.
For interplanetary missions, delta-v is often plotted on a porkchop plot, which displays the required mission delta-v as a function of launch date.

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1. ### Why is the integrated velocity times change in velocity zero?

So consider a subject system, a galaxy, with stars in it. This galaxy is passed by another object, the perturber. When the interaction is fast, we call this interaction a high-speed encounter. Now we consider that the interaction is really fast. This means that during the interaction, the...
2. ### I How is the weak force related to a change in velocity?

Hi everyone, The four fundamental forces are gravity (I understand that G.R. does not look upon gravity as a force but I'm not worried about that here), the Lorentz force, the weak force, and the strong force. I'm familiar with the inverse square law for gravitation and the Lorentz force...
3. ### Finding the change in velocity through a potential difference

We're given the equation qB=mv/r which is simple enough. I just don't know how to find the velocity given the acceleration through a potential difference. I tried using the radial acceleration equation given to me but I end up with the square root of a negative...and that breaks math... I...
4. ### Finding the change in velocity from an acceleration vs time graph

Homework Statement The graph shows the variation with time t of the acceleration a of an object (graph attached). What is the change in velocity of the object in the time interval 0 to 4s? Homework Equations a = v/t The Attempt at a Solution My initial answer was -8 m/s, by simply finding the...
5. ### Can instantaneous velocity be different from average velocity?

Homework Statement Is it possible for the instantaneous velocity of an object at some time, t1, to not be parallel to the average velocity over a short time interval, Δt=t2-t1? If it is not possible, explain why not. If it is possible, explain what this situation implies about the motion of...
6. ### Uncharged particle in a magnetic field suddenly gets charged

What happens to the velocity? Say we have a piece of space debris in free fall. It has a particular velocity at a given time. Then say at some later time it's bombarded with ionic gas or something that causes it to become charged. Does the velocity change? My guess would be yes, because the...
7. ### Is Velocity Increasing or Decreasing with Negative Acceleration?

Good afternoon all, For those of you that teach physics, if an object has an initial velocity of - 5m/s and a final velocity of -20 m/s, do you consider the velocity to be increasing or decreasing in this case? I view this to be strictly defined mathematically, that is that the acceleration is...
8. ### How Does Change in Velocity Relate to Vector Subtraction?

Homework Statement Homework EquationsThe Attempt at a Solution [/B] Assuming the right direction is positive, it hits the wall and reaches point 2, so to get back to point 1, it's in a negative direction, so it should be MINUS 4m so option A but the correct answer is B?? Or is it to do...
9. ### E=1/2mv^2 Given E and change in velocity

Homework Statement It takes 185 kJ of work to accelerate a car from 23.0 m/s to 28.0 m/s. What is the car’s mass?Homework Equations E=1/2mv^2 The Attempt at a Solution I get that I must put (2E) over V2 I am just not sure if I was allowed to put the change in velocity so it would look like...
10. ### Change in velocity due to force acting over given time

What change in velocity would be produced by an unbalanced force of 2.4 × 10^4 N acting for 6 s on a 2.0 × 10^3 kg dragster? Not sure how to setup this problem Equations i have are as follows: Fnet = mass × acceleration Velocity2 = velocity1 + acceleration × time Distance = velocity1 × time +...
11. ### Change in Velocity after a Collision

Homework Statement Kevin and Jake collide in the air. If Kevin undergoes a 4.2 kg*m/s change in momentum, what is Jacob’s change in velocity if he has a mass of 83.2 kg? Homework Equations p=mv MV+mv=MV'+mv' The Attempt at a Solution I tried the simplest way possible... p=mv v=p/m v=4.2/83.2...
12. ### Conservation of Momentum in Weightless Environments

Homework Statement If an astronaut was in a weighless environment, sitting down and eating a meal, what would happen to the astronaut if the spacecraft decided at that moment to turn on the space craft's main engines and a) the astronaut was facing the engines? b) the astronaut's back was to...
13. ### Determine magnitude of change in velocity and direction

Homework Statement A sailing boat moves at 12ms-1 due North then changing direction to north-west and traveling at a speed of 5.5ms-1 . Determine the magnitude of change in velocity n its direction. Homework EquationsThe Attempt at a Solution
14. ### Delta v and change in velocity

If the velocity of the object of 5 kg changed from 5 m/s to 4 m/s. Then is the change in kinetic energy -22.5 J or +22.5J. doesn't change mean final velocity minus initial velocity?
15. ### Adding and Subtracting vectors; Finding change in velocity

Homework Statement A batsman hits a cricket ball traveling towards him at 30m/s over square leg at 50m/s. If the cricketer is facing north and square leg is west of him, what is the change in velocity of the ball? Homework Equations Δv= Final velocity subtract initial velocity. The...
16. ### Need help finding change in velocity and momentum

An automobile of mass 1500 kg traveling at 24 m/s crashes into a similar parked automobile. The two automobiles remain joined together after the collision. Suppose that the collision last for 0.020s, and pavement with a coefficient of friction uk=0.63. What change of momentum and what change of...
17. ### How to find Change in velocity on an Acceleration vs TIme Graph?

Homework Statement The question is: Acceleration versus time graphs for five objects are shown below. All axes have the same scale. Which object had the greatest change in velocity during the interval?2. The attempt at a solution Not sure how to start here I only know about distance over time...
18. ### Solving Impulse: Why Only 1 Method Works for Determining Change in Velocity

Homework Statement A ball of mass 0.150 kg is dropped from rest from a height of 1.25 m. It rebounds from the floor to reach a height of 0.960 m. What impulse was given to the ball by the floor? Homework Equations Δmv/t =I vf^2=vo^2 +2aΔy The Attempt at a Solution mghi =...
19. ### Change in Velocity Homework: Solving the Vector Difference

Homework Statement A car's velocity changes from 13.9 m/s east to 12.8 m/s northeast. What is the change in it's velocity? It's a 4 marker. Homework Equations The Attempt at a Solution Honestly, I don't really know how to start this. I know it's a vector difference and I've drawn...
20. ### How Do You Calculate the Change in Velocity of a Tennis Ball?

Change in velocity, help please. :) Homework Statement A tennis ball’s initial velocity is 30 m/s [S]. When struck by a tennis racquet, its velocity becomes 28 m/s [N30°W]. Determine the ball’s change in velocity. The Attempt at a Solution I've used the normal component method but I end up...
21. ### Change in velocity when given a graph that shows time and acceleration

Homework Statement The graph in the figure describes the acceleration as a function of time for a stone rolling down a hill starting from rest. Find the change in the stone's velocity between 2.5s and 7.5s. Homework Equations I think v = v0t +1/2at^2 The Attempt at a Solution I honestly...
22. ### Location of minimum change in velocity for orbit escape

Homework Statement A rocket is in elliptic orbit about the earth. To put it into escape velocity, its engine is fired briefly, changing the rocket’s velocity by deltaV . Where in the orbit, and in what direction, should the firing occur to attain escape with a minimum value of deltav...
23. ### Conservation of momentum, change in velocity due to added mass from above

Homework Statement A 15 kg cart is moving east at 3.0 m/s when 10 kg of newspaper is vertically dropped into the cart. Find final veocity?[b]2. Homework Equations [/b m1v1i+m2v2i=m1v1f+m2v2f Kinematic eqs and trig will be necessary to find components for the 10kgnewspaper The Attempt at a...
24. ### Angular momentum and change in velocity

Homework Statement A turntable has a moment of inertia of 2.5 x 10-2 kg m2 and spins freely at 33.3 rev/min. A 0.25 kg ball of putty is dropped vertically on the turntable at a point 0.20 m from the center. What is the new angular speed of the system? a. 41 rev/min b. 24 rev/min c. 33...
25. ### Angular change in velocity (momentum)

Homework Statement A merry-go-round has a radius of 3.0 m and a rotational inertia of 600 kg m2. The merry-go-round is initially at rest. A 20 kg child is running at 5.0 m/s along a line tangent to the rim. Find the angular velocity of the merry-go-round after the child jumps on. a. 0.38...
26. ### Change in Velocity: avg & difference in initial & final velocities

1. If the velocity at the beginning of an interval is 4 m/s and at the end of the interval it is 10 m/s, then what is the average of these velocities, and what is the change in velocity? Give an example of positive initial and final velocities for which the order of the four quantities...
27. ### Speed, change in velocity, and average acceleration

Homework Statement At t = 0, an automobile traveling north begins to make a turn. It follows one-quarter of the arc of a circle of radius 10.5 m until, at t = 1.42 s, it is traveling east. The car does not alter its speed during the turn. Find the car's speed. Find the change in it's velocity...
28. ### Change in velocity of light with change in optical density

hey guys! we know that velocity of a wave = wavelength x frequency. and speed of light changes with change in optical density. so there must be change in either frequency or wavelength or both. which of these quantities change with change in optical density? and why?
29. ### Minimum change in velocity Helpppp?

Minimum change in velocity! Helpppp? Homework Statement Calculate the minimum change in velocity (delta V or ∆V) required for the Space Shuttle to decrease its altitude to 60 miles if it’s orbiting with an apogee of 236 miles and a perigee of 215 miles above the surface of Earth. Use the...
30. ### The change in velocity betwen two points

Here's a question that I got in my mechanics tutorial. -------------------------------------------------------------------- A particle travels on a semi-circular path from A to B - The diameter being 200m, the time taken 80 seconds, Calculate: a) its speed b) average velocity from...
31. ### The Change in velocity and direction.

Homework Statement What is the acceleration of a bullet that was shot at 40.m/s in the horizontal and then changed to a velocity of 44.5m/s at 26.1* below the horizontal in a time of 2.0 seconds. Homework Equations vf-vi= delta v a= delta v / time The Attempt at...
32. ### Vectors (?), Change in Velocity, Average Accel.

Nice to meet you all. While this may be my first post here, I will be here quite often for the next year because I'll be taking physics. Homework Statement John drives 15 km directly west from Orion to Chester at a speed of 86 km/h, then directly south for 7.0 km to Seiling at a speed of...
33. ### Calculating change in velocity with resistance

Hi everyone, I'm a doctor who is fair at maths - haven't done physics for a while. I'm trying to model some heart physiology which I can describe as a mechanics problem: I have a particle, mass m, with a constant force acting on it, f. It also has resistance R, where the resistance is...
34. ### Change in velocity of air due to fan

Ok i have the following problem, I have a fan connected to the nozzle, i am given the nozzle area and the volumetric flow rate generated by the fan. How can i find the velocity of the air at different distances from the tip of the nozzle? any help is greatly appreciated
35. ### Change in Velocity Homework Solution

Homework Statement Water enters and leaves a pipe as shown at a steady speed of 1.5. Find the change in velocity. http://kv8v6q.blu.livefilestore.com/y1pjsZ-s4z6_sTZEgW2-nsZ8pf1YrZml2cqcsXxgwnDNbUzFlaPXJcSe_nX93qAi6xd_Z7BATO9oBNXPDbxrGoJHEkk6WbzV3wR/0.bmp Homework Equations...
36. ### Calculate Change in Velocity: 5.02N, 4kg, 23.3s, 116.966N*s

Homework Statement a force of 5.02N acts on a 4kg object for 23.3s. momentum is 116.966 N*s Homework Equations what is the change in velocity?
37. ### Calculating Change in Velocity of Ball from E to S

Homework Statement The initial velocity of a ball is 1.0 m/s East (E). The final velocity is 1.0 m/s South (S). The change in the velocity of the ball is? Homework Equations (x^2+y^2)^.5 The Attempt at a Solution would it simply be 1.4 southeast?
38. ### Change in velocity, average acceleration

Homework Statement Earth's orbit around the SUn is nearly circular. THe period is 1 year = 365.25 days. In an elapsed time of 2.70 days, what is Earth's angular displacement? what is the change in Earth's velocity (perpendicular to the average velocity) What is the Earth's average acceleration...
39. ### Change in Velocity: Find Solution and Reasoning

Homework Statement I am required to find the change in velocity given these two vectors: Va = 4.4 m/s [E31*S] Vb = 7.8 m/s [E25*N] Homework Equations delta V = Vb - Va delta V = Vb + (-Va) The Attempt at a Solution I am stuck between two solutions: #1. Simply subtracting...
40. ### Calculating Change in Velocity for a Baseball Player's Slide

The following diagram shows the path taken by the center of mass of a baseball player sliding along the ground in an attempt to make the base. The player is moving at a speed of 10m/s just before the slide and his speed 0.5 seconds later is 8.0m/s. The mass of the player is 80kg 1a)...
41. ### How do i calculate change in velocity?

Homework Statement An airplane is flying at 2.00 x 10^2 km/h [S30.0W]. It makes a smooth wide turn and heads east at 2.00 x 10^2 km/h. Find its change in velocity. Homework Equations v = vf - vi The Attempt at a Solution the directions are throwing me off. What do i do after i...
42. ### Spacecraft orbiting sun, change in velocity

Homework Statement A spacecraft is initially in a circular orbit of the sun at the Earth's orbital radius. It uses a single brief rocket thrust parallel to it's velocity to put it in a new orbit with aphelion distance equal to the radius of Jupiter's orbit. What is the ratio of the...
43. ### Size and direction of the change in velocity

Homework Statement Find Size and direction of the change in velocity: a)5m/s west to 10 m/s west b)10m/s west to 5m/s west c)5m/s west to 10m/s east Homework Equations The Attempt at a Solution a)10-5= 5 west b)5-10=-5 because there isn't size wihe negitve the...
44. ### Calculate the Change in Velocity of a Van

can anyone help me: a van is traveling north at a speed of 28ms-1. after turning a corner its heading is 40 degrees east of north at 25ms-1. workout the change in velocity of the van
45. ### What is the direction of the change in velocity of the ball?

9 A softball of mass 0.15 kg traveling at a speed of 16 m s–1 is struck so that it moves away from the bat at an angle of 45° to its original direction and with the same speed. a What is the direction of the change in velocity of the ball? how do u work this question out ? the book told...
46. ### Calculating Change in Velocity of 600kg Sports Car

2) the driver of a 600kg sports car, heading directly for a railroad crossing 250m away, applies the brakes i a panic stop. the car is moving at 40m/s, and the brakes can supply a friction force of 1200N. a) how fast is the car moving when it reaches the crossing? - i tried finding the change...