# Physics/mechanics, forces accelaration

• gaz3992
In summary, a ball is thrown horizontally out of a window 18m above the ground with a velocity of 5.0ms. Using the equation S=ut+1/2at^2, where u=0, a=9.8, and s=18, it takes approximately 2 seconds for the ball to drop. The horizontal velocity does not affect the time taken to drop. Further calculations may use the horizontal velocity, such as finding the distance the ball lands from the window.
gaz3992

## Homework Statement

A ball is thrown horizontal out of a window 18m above the ground. it is thrown horizontally at 5.0ms. show that it takes about 2 seconds to drop.

S=ut+1/2at^2

## The Attempt at a Solution

u=0
a=9.8
s=18
18=0t+1/2*9.8t^2
36=9.8t^2
sqrt3.6734=t
t=1.92

is this near enough too 2 to be the right answer or have i made a mistake some where i was not sure if the horizontal force would have any effect on the time taken to drop. Any help would be much appreciated.

That's perfect. 1.92 is certainly "about 2 seconds" in anyone's book!
The horizontal component of the ball's motion is independent of the vertical, gravitational, component; so your method is fine.
(That horizontal velocity of 5m/s doesn't come into this calculation, but is probably needed for further calculations, such as how far away from the window does the ball land?)

Oh, and welcome to Physics Forums!

Thanks i just needed conformation because i got to the answer partially using trial and error to find the right method and I'm impressed you managed to guess the exact next question on the paper.

## 1. What is the difference between speed and velocity?

Speed refers to the rate of motion of an object, while velocity indicates the speed and direction of an object's motion. In other words, velocity includes both the magnitude (speed) and the direction of an object's movement, while speed only refers to the magnitude.

## 2. How do forces affect an object's motion?

Forces can either change the speed or direction of an object's motion, or both. When a force acts on an object, it can cause the object to accelerate or decelerate, depending on the direction of the force. The greater the force applied, the greater the change in the object's motion.

## 3. What is the relationship between mass and acceleration?

According to Newton's Second Law of Motion, the acceleration of an object is directly proportional to the net force acting on the object and inversely proportional to its mass. This means that the greater the mass of an object, the more force is needed to accelerate it at the same rate as a smaller object.

## 4. Can an object have a constant acceleration?

Yes, an object can have a constant acceleration if the net force acting on it remains constant. This is known as uniform acceleration. A common example of an object with constant acceleration is a falling object under the influence of gravity, where the acceleration due to gravity remains constant.

## 5. What is the difference between weight and mass?

Mass refers to the amount of matter in an object and remains constant regardless of the object's location. On the other hand, weight is a measure of the force of gravity acting on an object and can vary depending on the object's location in the universe. Mass is typically measured in kilograms, while weight is measured in newtons.

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