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# kinematics - find the initial velocity Watch

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1. Could anyone please explain how to get the answer for the following question:

A ball is thrown vertically upwards and travels freely under gravity. Three seconds later it has a speed of 4.4ms^-1 but its direction has changed. Find the initial velocity of the particle.

S = -
U = -
V = 4.4 ms^-1
A = -9.8ms^-2
T = 3 seconds

Keep getting -0.15 but the actual answer is 25?
2. If we break down the question into parts, it might be more useful

(Original post by u.sha)
A ball is thrown vertically upwards and travels freely under gravity.
This tells us that acceleration (a) = acceleration due to gravity in the opposite direction ()

(Original post by u.sha)
Three seconds later
This tells us that time (t) is equal to three seconds.

(Original post by u.sha)
Three seconds later it has a speed of 4.4ms^-1 but its direction has changed.
As the final velocity is in the opposite direction to the initial velocity; The final velocity (v) =

(Original post by u.sha)
Find the initial velocity of the particle.
This means that the question wants us to find out our initial velocity (u).

Jotting down all we know:

s = -
u = ?
v =
a =
t =

Using the constant acceleration formula , we rearrange to make u the subject.

Then we input our values to get:

Therefore, the initial velocity is equal to
3. (Original post by u.sha)
Could anyone please explain how to get the answer for the following question:

A ball is thrown vertically upwards and travels freely under gravity. Three seconds later it has a speed of 4.4ms^-1 but its direction has changed. Find the initial velocity of the particle.

S = -
U = -
V = 4.4 ms^-1
A = -9.8ms^-2
T = 3 seconds

Keep getting -0.15 but the actual answer is 25?
i love norogami
4. (Original post by drinktheoceans)
If we break down the question into parts, it might be more useful

This tells us that acceleration (a) = acceleration due to gravity in the opposite direction ()

This tells us that time (t) is equal to three seconds.

As the final velocity is in the opposite direction to the initial velocity; The final velocity (v) =

This means that the question wants us to find out our initial velocity (u).

Jotting down all we know:

s = -
u = ?
v =
a =
t =

Using the constant acceleration formula , we rearrange to make u the subject.

Then we input our values to get:

Therefore, the initial velocity is equal to
omg yes yes yes this makes sense now thank you!!

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Updated: October 1, 2016
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