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Mechanics
Mechanics is the branch of physics that deals with the interactions of objects and forces in the observable world. Questions asking about projectile motion, conservation of energy, and calculus based mechanics are perfect for this topic, but questions about repairs that a mechanic would do belong in our vehicles categories.
2,416 Questions
Unbalanced forces in volleyball?
Unbalanced forces are important in order to move anything. An object under balanced forces does not move. For example as you sit in your chair reading this, gravity is exerting a force on your body downwards but your chair balances this force by exerting a force upwards on you that is equal and opposite to the force of gravity. These two forces oppose each other and therefore you do not move. In tennis in order to change the direction of a tennis ball you need to exert a net force(an unbalanced force) in the direction you want the tennis ball to move. In tennis there are also unbalanced torques(a force acting at a distance from a pivot point) on the ball that cause the ball to spin. Hope that helps.
Does shape affect air resistance on an object?
Yes it does. Friction tends to slow down objects in motion, like if you throw a brick through the air, it will not go far, depending on the force you used to throw the brick. Its speed will gradually decline due to the brick's friction with air. Now if you threw a football through the air using the same force that you used to throw the brick, it will go a lot farther than the brick because of its shape. The blunt edge of the football makes it easier to 'slice' through the air, thus creating less friction. It is the same aspect with the shape of a car. The front of the car is blunt, so it will 'cut' through the air without much friction.
find a materials with a high coefficient of static friction and use them against each other ( like rubber dry concrete ) and bound them to the object and the surface it rests on. Increase the normal force by adding mass on the object or applying a perpendicular force to the surface of the object.
I'm Laica Mae Montillano
1st year section 1
I'm studying at San Antonio National High School
Angle between force and displacement to get minimum work?
The work done by a force is the dot product of the force and the displacement of the point of application of the force i.e.
component of force in the direction of displacement * displacement
or
component of displacement in the direction of force * force
let W be the work done. Then :
W = F.S
W = |F|*|S|*cos(θ) ---- equation 1
where F and S are force and displacement in vector form and |F|, |S| are their magnitudes respectively. cos(θ) is the angle between line of action of force vector and displacement vector.
It is clear from the equation 1 that work will be minimum when cos(θ) is minimum. It is known from trigonometry that minimum value of cos(θ) is -1 which is for angle 1800 or π radians. So work done will be minimum when angle between force and displacement vector is π radians or 1800 i.e. when point of application of force is displaced exactly opposite to the direction of application of force.
I appreciate the last attempt to answer the question, but I think it is wrong. The answer should be 90°, because although cos180° = -1, the negative sign in
- FScos180° only signifies that the work done has taken away energy from the system, or it signifies that the work is done in the opposite direction, implying that work is done. When the angle is 90°, on the other hand, work done = 0, ie, no work is done at all. Thus the answer should be 90°.
(The above answers define minimum work differently.
The first answers is if minimum work is negative work, therefore if you do work in the opposite direction of the displacement, the work you do is negative and is less than 0. Minimum work here is the work that is the lowest number.
The second answer defines minimum work as the magnitudeof the work done being minimized. Since magnitude is always positive, minimum work in this case would always be zero. Which one is correct depends on the situation you are dealing with.)
What is the wave length of a sound wave?
That all depends on the frequency of the sound and its speed in whatever substance
it happens to be traveling through.
In air, the wavelength of audible frequencies ranges from about 17.1 millimeters to
about 17.1 meters.
(20-20K Hz, 343 m/s)
Different standard units of force and momentum and impulse?
Force = mass x acceleration = kg(m/s^2) or N
Momentum = mass x change in velocity = kg(m/s) or Ns
The units of impulse are the same as momentum's because impulse is just the change in momentum.
the maximum value of limiting friction is = coff. of static fric. * normal force.
in this case normal force =mgcosA=17N.
the coff=0.5 so the maximum friction=0.5*17=8.5N.
but the force acting downward on the incline is mgsinA which is =2*10*0.5=10N.
as it has breached the value of friction,the block will move.now kinetic fric. will act.As the coff. of kinetic fric.=0,the surface is as good as a frictionless one.use the laws of kinematics to find the velocity(v=u+at,a=gsinA,t=3,u=0)
hence the answer is=15m/s.
in reality if there is a coff of static fric,ther ewill be a coff.of kinetic fric.
good luck.
regards
carlitos tevez.
Sound travels at different speeds depending on the medium it is traveling through. In air at room temperature, sound travels at approximately 343 meters per second. In water, sound travels faster at around 1,480 meters per second. In steel, sound can travel even faster at about 5,960 meters per second.
Give an example of an object that has no net force acting on it?
Kinetic Energy is the energy of motion, so anything that is moving has kinetic energy.
Examples :
a ball rolling down a ramp
a spoon falling off a table
a baseball hurtling towards a window
a moving train
a coin falling from the roof of a building
(generally anything with a rest mass which isn't at rest)
If a rock falls from a cliff for 9 seconds how fast is it going when it reaches the bottom?
Assuming that no net external forces are taking place, such as friction or air resistant, the only force acting upon the falling rock would be gravity. Using one of the kinematic equations, we can solve for the final velocity of the rock:
v(final) = v(initial) + at
We can substitute 0 for "v(initial)" since the rock is starting from rest. We can also substitute 9.81 meters per second squared for "a", which is the gravitational acceleration on Earth. Finally, we can substitute 9 seconds for "t". This gives us:
v(final) = 0 + (9.81)(9)
v(final) = 88.29 meters per second.
With an open orbit, the object never returns. Examples would be a satellite in an unstable (open) orbit crashing down on Earth or a passing comet on a hyperbolic orbit which will leave our solar system (ejection loss).
Closed orbits are the stable, planet-like orbits where objects return in a predictable manner.
How is fluid used to lift heavy objects?
Water helps lift an objects via the buoyancy force. The buoyancy force is equal to the weight of water displaced by the volume of the submerged object. If this buoyancy force is equal to the weight of the object, the object will float in that position. If the object is completely submerged and the resulting buoyancy force is less than the weight of the object, it will continue to sink.
Determine the net force on a car moving in a straight line at constant speed?
If traveling at constant speed in a constant direction then net force is zero as
there is no acceleration. Acceleration would change one or the other, or both.
F = ma = m (0) = 0
What force acts on the bowling ball?
The force that acts on a bowling ball is gravity pulling it downward towards the center of the Earth. Additionally, when the ball is thrown or rolled, external forces such as friction and air resistance will also act on it.
Capacity ratio of a heat exchanger?
It is the ratio of (mdot*Cp)min/(mdot*Cp)max where the heat exchanger contains two fluids for which the mdot*Cp should be calculated for each to determine which one is greater. by doing so one can define the ability of one fluid to carry thermal/heat energy with respect to the other. so this is a way of saying how well can heat be transferred and so how effective is the heat exchanger
Does a solid have definite mass?
Yes, a solid has a definite mass because the mass of a solid is determined by the total amount of matter it contains, which remains constant regardless of its shape or volume.
none of the above
Force centripetal = (mass * velocity^2) ÷ radius
More mass , more force needed to keep object in the circle
Object going faster, more force needed to keep object in the circle
Larger radius, less force needed to keep object in the circle
That is why mass and velocity are in the numerator ( multipliers)
and Radius is in the denominator ( divider)
How much distance traved in feet after 12 seconds at 87 miles per hour?
In 12 seconds, a car traveling at 87 miles per hour covers 211.2 feet. This is calculated by converting 87 miles per hour to feet per second, then multiplying by the time in seconds.
How fast was Barry Sanders in mph?
Barry Sanders ran a 40-yard dash in about 4.37 seconds, which would be roughly 20 mph. However, this speed may not accurately reflect his full top speed during a game.
Does net force allows you to stand up from a chair?
Yes, the net force is needed to stand up from a chair. When you push against the chair with a force greater than the force of gravity pulling you down, the net force becomes positive and allows you to rise. Without a net force, you would remain seated.
How fast does an object need to move to break the speed of sound?
Light travels at 186,000 miles per second, which means you have to travel faster than that to break the light barrier. This feat is technically "impossible", since the faster you move, the more mass you have and the more mass you have, the more energy is required to move you, and by the time you reach the speed of light, you will need to have infinite energy. This doesn't apply to light particles, since they have no mass.
At 500 mph, it would take an airplane 4 hours to fly 2000 miles.
20 minutes to drive between two towns average speed 45 miles per hour how far apart are these towns?
The distance between the two towns is 15 miles. This is determined by multiplying the average speed (45 miles per hour) by the time it takes to drive between the towns (20 minutes converted to hours is 1/3 hour). 45 miles/hour x 1/3 hour = 15 miles.
How does the shape of an object affect how fast it falls?
Different shapes result in different resistances (force opposing gravity) on the object as it falls. An object will continue to accelerate as it falls, until the gravitational force is equivalent to this resistance. This is known as "Terminal Velocity." The lower the resistance is, the higher the resulting speed will be before this equilibrium is reached.
An object with a large surface area or volume (high wind resistance value) and low density (low gravitational force) will fall slower than an object that has a lower surface area (low wind resistance) with a higher density (high gravitational force).
e.g., A large hollow Styrofoam ball will fall much slower than a metal dart.
What fields of science study machines?
Fields of science that study machines include robotics, mechanical engineering, computer science, and artificial intelligence. These disciplines investigate the design, development, and functioning of machines to improve their efficiency, intelligence, and capabilities.
