Find initial velocity given acceleration & distance, no time

In summary, to find the initial speed of a frog jumping 1m in the air without air resistance, use the equation V2 = 2 a d. In this case, the acceleration is -9.8m/s^2 and the distance is 1m. By plugging in these values, the initial speed can be calculated as 4.43m/s.
  • #1
brendonsushi
1
0

Homework Statement


Frog jumps in air to 1m height. Neglecting air resistance find initial speed the instant it leaves the ground.
a= -9.8m/s^2
d= 1m
vi=?

Homework Equations


d=1/2(vf+vi)t
d=1/2at^2 + vi(t) + di

The Attempt at a Solution


I figured that since acceleration is 9.8m/s, I could just find time by dividing 9.8m/s by 9.8 and that would give me 1m/0.1s, but that doesn't seem quite right. I then proceeded to put the acceleration, distance, and "time" values into d=1/2at^2 + vi(t) + di, so that vi=0.9m/s^2, but I don't think I did it right. Is there any way to just find initial velocity with only acceleration and distance values?
 
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  • #2
Hi brendon:

I think you are missing a useful equation. V2 = 2 a d.

Hope this helps.

Regards,
Buzz
 

1. What is initial velocity?

Initial velocity (also known as initial speed) is the starting velocity of an object at the beginning of its motion. It is usually denoted by the symbol "u".

2. How do you calculate initial velocity given acceleration and distance?

The formula for calculating initial velocity is: u = √(v2 - 2ad), where u is the initial velocity, v is the final velocity, a is the acceleration, and d is the distance traveled. If the final velocity is not known, you can use the formula v = u + at to solve for v first.

3. Why is time not needed to find initial velocity in this scenario?

In this scenario, we are assuming that the object starts from rest and accelerates to its final velocity over a certain distance. Since we know the distance and acceleration, we can use the formula d = ut + 1/2at2 to eliminate the time variable and solve for u.

4. Can initial velocity be negative?

Yes, initial velocity can be negative if the object is moving in the opposite direction of the positive direction. This indicates that the object is moving backwards or decelerating.

5. Are there any real-life applications for finding initial velocity given acceleration and distance?

Yes, there are many real-life applications for this calculation, such as calculating the launch speed of a projectile, determining the takeoff speed of an airplane, or finding the initial speed of a car in a collision. It is also commonly used in physics experiments and in engineering calculations.

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