An ordinary pulley has an MA of 1; it only changes the direction of the force and not its magnitude. Combinations of pulleys, such as those illustrated in
[link] , are used to multiply force. If the pulleys are friction-free, then the force output is approximately an integral multiple of the tension in the cable. The number of cables pulling directly upward on the system of interest, as illustrated in the figures given below, is approximately the MA of the pulley system. Since each attachment applies an external force in approximately the same direction as the others, they add, producing a total force that is nearly an integral multiple of the input force
$T$ .
Section summary
Simple machines are devices that can be used to multiply or augment a force that we apply – often at the expense of a distance through which we have to apply the force.
The ratio of output to input forces for any simple machine is called its mechanical advantage
A few simple machines are the lever, nail puller, wheelbarrow, crank, etc.
Conceptual questions
Scissors are like a double-lever system. Which of the simple machines in
[link] and
[link] is most analogous to scissors?
Suppose you pull a nail at a constant rate using a nail puller as shown in
[link] . Is the nail puller in equilibrium? What if you pull the nail with some acceleration – is the nail puller in equilibrium then? In which case is the force applied to the nail puller larger and why?
Explain why the forces in our joints are several times larger than the forces we exert on the outside world with our limbs. Can these forces be even greater than muscle forces (see previous Question)?
What is the mechanical advantage of a nail puller—similar to the one shown in
[link] —where you exert a force
$\text{45 cm}$ from the pivot and the nail is
$\text{1.8 cm}$ on the other side? What minimum force must you exert to apply a force of
$\text{1250 N}$ to the nail?
Suppose you needed to raise a 250-kg mower a distance of 6.0 cm above the ground to change a tire. If you had a 2.0-m long lever, where would you place the fulcrum if your force was limited to 300 N?
a) What is the mechanical advantage of a wheelbarrow, such as the one in
[link] , if the center of gravity of the wheelbarrow and its load has a perpendicular lever arm of 5.50 cm, while the hands have a perpendicular lever arm of 1.02 m? (b) What upward force should you exert to support the wheelbarrow and its load if their combined mass is 55.0 kg? (c) What force does the wheel exert on the ground?
A typical car has an axle with
$1\text{.}\text{10 cm}$ radius driving a tire with a radius of
$\text{27}\text{.5 cm}$ . What is its mechanical advantage assuming the very simplified model in
[link] (b)?
If you used an ideal pulley of the type shown in
[link] (a) to support a car engine of mass
$\text{115 kg}$ , (a) What would be the tension in the rope? (b) What force must the ceiling supply, assuming you pull straight down on the rope? Neglect the pulley system’s mass.
you shouldn't say distance,displacement and distance are two different things .distance can be lopped curved but displacement is always in a straight line so you can't use distance to define it. displacement is the change of position in a specified direction.
Since you said they have the same momentum.. So meaning that there is more like an inverse proportionality in the quantities used to find the momentum. We are told that the the is a larger mass and a smaller mass., so we can conclude that the smaller mass had higher velocity as compared to other one
Gift
Mathamaticaly correct
megavado
Mathmaticaly correct :)
megavado
I have proven it by using my own values
Gift
Larger mass=4g
Smaller mass=2g
Momentum of both=8
Meaning V for L =2 and V for S=4
Now find there kinetic energies using the data presented
Gift
grateful soul...thanks alot
Faith
Welcome
Gift
2 stones are thrown vertically upward from the ground, one with 3 times the
initial speed of the other. If the faster stone takes 10 s to return to the ground, how
long will it take the slower stone to return? If the slower stone reaches a maximum
height of H, how high will the faster stone go
Suppose that a grandfather clock is running slowly; that is, the time it takes to complete each cycle is longer than it should be. Should you (@) shorten or (b) lengthen the pendulam to make the clock keep attain the preferred time?
shorten it, since that is practice able using the simple pendulum as experiment
Silvia
it'll always give the results needed no need to adjust the length, it is always measured by the starting time and ending time by the clock
Paul
it's not in relation to other clocks
Paul
wat is d formular for newton's third principle
Silvia
okay
Silvia
shorten the pendulum string because the difference in length affects the time of oscillation.if short , the time taken will be adjusted.but if long ,the time taken will be twice the previous cycle.