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3 years ago

A stone is thrown vertically upward with an initial speed of 5 m/s. What is the velocity of the stone 3 seconds later?

Physics

2 answers:

Alina [70]3 years ago

8 0

Answer:

-25m/s

Explanation:

For motion under gravity:

I. For a body falling from a particular height the equations are:

a. V = u + gt

b. v2 = u2 + 2gh

c. h = ut + 1/2gt2

II. For a body thrown vertically upwards the equations become:

a. V = u – gt

b. v2 = u2 – 2gh

c. h = ut – 1/2gt2

Where v = final velocity in m/s, u= initial velocity in m/s, h= height in m, t= time in secs, g= acceleration due to gravity = 10m/s2.

Using,

v = u - gt

Where u = 5m/s, g = 10m/s2, t = 3s

v = 5 - 10 x 3

v = 5 - 30

v = -25m/s

The negative value of v means it's downward, that is, in the opposite direction of the motion.

Note that the approximate value of 'g' was taken as 10m/s2 since the value wasn't given. You should use the value of 'g' given you to solve.

uysha [10]3 years ago

6 0

Answer:

$v_f=-24.4\frac{m}{s}$

Explanation:

The acceleration due to gravity is in the downward direction. This means that it will oppose the upward motion of the stone. This will cause the stone to stop and begin to fall. Therefore, the sign of the final velocity is negative, since it is in the downward direction. The final velocity is given by:

$v_f=v_0+gt\\v_f=5\frac{m}{s}+(-9.8\frac{m}{s^2})(3s)\\v_f=-24.4\frac{m}{s}$

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Archy [21]

Answer:

a) t = 1.8 x 10² s

b) t = 54 s

c) t = 49 s

Explanation:

a) The equation for the position of an object moving in a straight line at constan speed is:

x = x0 + v * t

where

x = position at time t

x0 = initial position

v = velocity

t = time

In this case, the origin of our reference system is at the begining of the sidewalk.

a) To calculate the time the passenger travels on the sidewalk without wlaking, we can use the equation for the position, using as speed the speed of the sidewalk:

x = x0 + v * t

95 m = 0m + 0. 53 m/s * t

t = 95 m/ 0.53 m/s

t = 1.8 x 10² s

b) Now, the speed of the passenger will be her walking speed plus the speed of th sidewalk (0.53 m/s + 1.24 m/s = 1.77 m/s)

t = 95 m/ 1.77 m/s = 54 s

c) In this case, the passenger is located 95 m from the begining of the sidewalk, then, x0 = 95 m and the final position will be x = 0. She walks in an opposite direction to the movement of the sidewalk, towards the origin of the system of reference ( the begining of the sidewalk). Then, her speed will be negative ( v = 0.53 m/s - 2*(1.24 m/s) = -1.95 m/s. Then:

0 m = 95 m -1.95 m/s * t

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Vinvika [58]

Answer:

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Explanation:

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