Calculating Time of a Ball Thrown with Velocity 39m/s | No Air Resistance

  • Thread starter physicsgurl12
  • Start date
  • Tags
    Velocity
In summary: D. 8s yay!In summary, using the equation y(t) = y_0 + v_{y0} t - \frac{1}{2} g t^2 for vertical motion under constant downward acceleration (like due to gravity), we can find that the time it takes for a ball thrown straight up with a velocity of 39m/s to hit the ground is 8 seconds with no air resistance.
  • #1
physicsgurl12
184
0

Homework Statement


A ball is thrown straight up with a velocity of 39m/s. how much time passes before the ball hits the ground. No air resistance.
4s-wrong
1.2s
2.4s
8s


Homework Equations



v=d/t a=v/t

The Attempt at a Solution


9.8/39= .02
39/9.8=3.97959
 
Physics news on Phys.org
  • #2
physicsgurl12 said:

Homework Statement


A ball is thrown straight up with a velocity of 39m/s. how much time passes before the ball hits the ground. No air resistance.
4s-wrong
1.2s
2.4s
8s


Homework Equations



v=d/t a=v/t

The Attempt at a Solution


9.8/39= .02
39/9.8=3.97959

It would be better if you started with the general equation for vertical motion (under constant downward acceleration, like due to gravity):

[tex]y(t) = y_0 + v_{y0} t - \frac{1}{2} g t^2[/tex]

If you start with that equation, you get two solutions for the time when the object is at ground level...
 
  • #3
berkeman said:
If you start with that equation, you get two solutions for the time when the object is at ground level...
Well, I hope at least one of them is at t=0... :biggrin:
 
  • #4
DaveC426913 said:
Well, I hope at least one of them is at t=0... :biggrin:

:wink:
 
  • #5
berkeman said:
It would be better if you started with the general equation for vertical motion (under constant downward acceleration, like due to gravity):

[tex]y(t) = y_0 + v_{y0} t - \frac{1}{2} g t^2[/tex]

If you start with that equation, you get two solutions for the time when the object is at ground level...

okay thanks for the equation . but i solved it out and got .1 ?
 
  • #6
physicsgurl12 said:
okay thanks for the equation . but i solved it out and got .1 ?

Nope.

Please show your work, and we'll see if we can spot the error...
 
  • #7
okay let's see. i guess i did. 0=39m/s*t-4.9t^2
4.9/39=.1256 yeah that's not even real algebra
 
  • #8
physicsgurl12 said:
okay let's see. i guess i did. 0=39m/s*t-4.9t^2
4.9/39=.1256 yeah that's not even real algebra

Almost there.

You should be solving for the time t, not 1/t...

Write out the algebra steps more clearly after that equation, and be sure to solve to for t.
 
  • #9
1.2??
 
  • #10
physicsgurl12 said:
1.2??

No.

Your equation here is correct:

0=39m/s*t-4.9t^2

Just solve it for t. You came close when you tried before. Show us each algebra step. There are two terms on the righthand side of the equation. How do you move one of them to the LHS of the equation? Can you then cancel anything out?

Solve for t.
 
  • #11
berkeman said:
0=39m/s*t-4.9t^2

Just solve it for t. You came close when you tried before. Show us each algebra step. There are two terms on the righthand side of the equation. How do you move one of them to the LHS of the equation? Can you then cancel anything out?

Solve for t.

0= 39m/s*t-4.9*t^2
4.9*t^2=39m/s*t
4.9*t=39m/s
t=7.959?
 
  • #12
physicsgurl12 said:
0= 39m/s*t-4.9*t^2
4.9*t^2=39m/s*t
4.9*t=39m/s
t=7.959?

Bingo!

So which multiple choice answer is correct?
 
  • #13
D. 8s yay!
 

FAQ: Calculating Time of a Ball Thrown with Velocity 39m/s | No Air Resistance

Why is velocity important in science?

Velocity is an important concept in science because it measures the rate at which an object changes its position in a certain amount of time. It helps scientists understand how objects move and predict their future movements.

What is the difference between speed and velocity?

While both speed and velocity measure how fast an object is moving, velocity also takes into account the direction of the movement. Speed is a scalar quantity, while velocity is a vector quantity.

How is velocity calculated?

Velocity is calculated by dividing the change in position (displacement) by the change in time. The equation for velocity is v = ∆x/∆t, where v is the velocity, ∆x is the change in position, and ∆t is the change in time.

What are the units for velocity?

The units for velocity depend on the system of measurement being used. In the International System of Units (SI), velocity is measured in meters per second (m/s). In the United States Customary Units, it is measured in feet per second (ft/s).

How does velocity affect acceleration?

Velocity and acceleration are closely related. Acceleration is the rate at which velocity changes. If an object's velocity is changing, it is also accelerating. The direction of an object's acceleration is determined by the direction of its velocity and the change in velocity over time.

Similar threads

Solving a Ball Thrown off a Cliff: How Long Does it Take?
Replies
4
Views
2K
Oblique soccer shot calculation task
2
Replies
38
Views
3K
Free falling ball with and without air resistance
Replies
3
Views
2K
Projectile Motion Problem: Kicking a soccer ball over a fence
Replies
11
Views
2K
Ball Release and Thrown to reach ground at the same time
Replies
1
Views
2K
Calculating Time of Flight & Velocity of a Ball Thrown Upwards
Replies
14
Views
2K
Calculating Final velocity and distance
Replies
14
Views
2K
Solving The Flight of a Ball: Examining Velocity & Time
Replies
2
Views
1K
Why is my time calculation for the ball's flight incorrect?
Replies
15
Views
5K
Projectile motion: Two Balls and Building
Replies
9
Views
2K

Hot Threads

Recent Insights

Back
Top