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Why does a projectile move upwards when thrown upwards even though a force of gravity acts downwards on it?
Wiki User
∙ 13y ago
In the act of "throwing", the thrower imparts an upward velocity to the object, by
temporarily applying an upward force to it that's greater than the downward force
of gravity. During that brief period, the sum of the forces on the object is directed
upward, so it accelerates in that direction. After the throwing ends, however, the
only force on the object is the force of gravity, directed downward, so its acceleration
is downward. That means that the upward velocity becomes smaller and smaller,
until it's zero at the peak of the arc, and the velocity then becomes downward as
the object begins to fall from its peak..
Wiki User
∙ 13y ago
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What quantities remain constant in projectile motion?
All that I can think of are: 1.) Gravity 2.) Wind 2.A) wind speed 2.B) direction of wind 3.) Angle of trajectory 4.) Initial speed of projectile 5.) Material through which projectile travels (as in density) 6.) Mass of projectile 7.) Spin 7.A) speed of spin 7.B) axis/axes spining occurs on 8.) Shape of projectile 9.) Temperature of medium projectile is in 10.) Size of projectile (as in height, width, and depth) 11.) Weighting of projectile 12.) Obsturctions to projectile's path In a vaccuum, though, these are the variables: 1.) Speed of object 2.) Obstructions in path 3.) Gravity
An object thrown or shot through the air is called what?
it is called a trajectory Projectile- the obect thrown though the air
Why do flames rise even though gravity pulls things downwards?
Hot gases expand and therefore are less dense than cold gases, and therefore hot gas has buoyancy and will rise, much as air bubbles float to the surface in water.
Do objects fall at the same speed through water?
No. The speed an object will fall in water depends on: 1) The mass of the object compared to the volume of water displaced 2) The hydrodynamic friction between the water and the objects motion 3) The local gravity. For example: A 10cm sphere of iron has a density of 7.8 and a mass of 4.08kg. The mass of water displaced is 0.52kg. Gravity exerts a downward force of 40.0N downwards on the sphere, while the water exerts an upwards force of 5.1N due to bouyancy. This means that there is an initial downward force of 34.9N downwards on the iron sphere. A 10cm sphere of glass has a density of 2.5 and a mass of 1.31kg. Gravity exerts a downward force of 12.8N downwards on the sphere, while the water exerts the same 5.1N upward bouyancy force. This means that there is an initial downward force of 7.7N downwards on the glass sphere. Both spheres will accelerate in water according to F=ma, where (F) is the force exerted, (m) is the mass and (a) is the acceleration. For the iron sphere, the initial acceleration is 8.6m/s2 while for the glass sphere the initial acceleration is 5.9m/s2. This difference is due to the bouyancy force of the water which is the same for both spheres, even though the masses are different. As the spheres accelerate, the drag force of the water will increase from zero to some value which equals the net gravity force calculated above. The drag coefficient will vary somewhat with the speed but it can be considered the same for both spheres if they are both the same smoothness. Since the forces are different, the steady state speed (terminal velocity) will be different for each sphere. A 10cm sphere of balsa wood has a density of 0.1 and a mass of 0.05kg. Gravity exerts a force of 0.5N downwards while the water exerts the same bouyancy force of 5.1N upwards. Thus the balsa sphere accelerates upwards rather than downwards because the water it displaces is heavier than it and squashes it up. It will have a terminal velocity in the upwards direction. By contrast, in a vacuum, there is no bouyancy force as nothing is being displaced so (F) is proportional to (m) and thus (a) is constant. In this case all the spheres would accelerate at the same speed. In our atmosphere, the bouyancy force of air is very small, so objects may appear to fall at the same rate when in fact they are very slightly different. A hydrogen sphere would rise in air, just like a balsa sphere rises in water.
Why there is no acceleration along x axis during projectile motion?
There is no force that acts upon the object in that direction. Gravity only acts on the y axis. Though there is some wind resistance that does cause a negative acceleration in the x direction. You are probably just being told to ignore this as it is usually negligible.
Why do the flames of a fire rise even though gravity pulls thing downwards?
The hot air is less dense so cold air rushes in to shove it upwards like a cork on water.
Flames of fire rise even though gravity pulls things downwards?
Yes. Fire goes upward precisely because Earth's gravity pulls things downward. The fire is lighter (less dense) than the air that replaces it, so the air pushes the hot air from the fire upwards.
Why do flames of a fire rise even though gravity pulls thing downwards?
It rises precisely due to gravity. The hot air in the flame is lighter (more precisely: it is less dense) than the surrounding colder air.
Why doesnt a ball sink into the ground?
Gravity. Sinkers go toward the ground faster because the spin put on them causes more air resistance on the top of the ball, pushing it downwards. Curve-balls and sliders also use air resistance to change direction or "break." A fastball stays straighter because the air resistance actually counter-acts gravity, pushing the ball upwards. Gravity is stronger though, and fastballs still sink a little bit.
Why at a campfire the ash from the burning wood goes up into the air instead of downwards even though gravity causes things to fall downwards?
Because the tiny ash particles ride in the flow of hot air rising from the fire ... same as the smoke particles do.
Why does ash from burning wood goes up into the air instead of going downwards even though gravity causes all things to fall downwards?
Air. Density. Lighter or less dense objects float. The ash floats on the hot (less dense) air.
What quantities remain constant in projectile motion?
All that I can think of are: 1.) Gravity 2.) Wind 2.A) wind speed 2.B) direction of wind 3.) Angle of trajectory 4.) Initial speed of projectile 5.) Material through which projectile travels (as in density) 6.) Mass of projectile 7.) Spin 7.A) speed of spin 7.B) axis/axes spining occurs on 8.) Shape of projectile 9.) Temperature of medium projectile is in 10.) Size of projectile (as in height, width, and depth) 11.) Weighting of projectile 12.) Obsturctions to projectile's path In a vaccuum, though, these are the variables: 1.) Speed of object 2.) Obstructions in path 3.) Gravity
Why is gravity more stronger than upthrust?
a) you have terrible grammar. It is "stronger" not "more stronger" b) Stronger than upthrust for what? A rockets upthrust is stronger than gravity, though for someone jumping, we dont exert enough force upwards to escape gravity. You should really think these things through more.
How does a simple pulley work?
A rope winds around the pulley so that two ropes hang downwards. Using one side of the rope to apply force causes the pulley to rotate and redirect the force, moving the load upwards even though the pull is applied downwards.
An object thrown or shot through the air is called what?
it is called a trajectory Projectile- the obect thrown though the air
Why do flames rise even though gravity pulls things downwards?
Hot gases expand and therefore are less dense than cold gases, and therefore hot gas has buoyancy and will rise, much as air bubbles float to the surface in water.
Why the flames of fire rise even though gravity pulls things downwards?
The hotter the air the less dense the molecules are so the rise. Just like in a thunderstorm, warm air is quickly thrust upward because of the pressure of the cooler, denser air. Gravity affects(pulls) the cooler, denser air more because it is heavier.
