Tag: machines

Quizzes (3) Questions (32)

Questions Related to machines

Multiple choice physics machines levers and pulleys pulley pulleys

A force of $250 N$ is required to lift a $75 kg$ mass through a pulley system. In order to lift the mass through $3 m$, the rope has to be pulled through $12m$. The percent efficiency of system is

  1. $50$

  2. $75$

  3. $33$

  4. $90$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Height lift was $h=3m$
Work done by the force is $W=Fd=250\times 12=3000Joule$

Work against the gravity i.e. $increase $ in potential energy of the  mass is $E=mgh=75\times 10\times 3=2250Joule $

so efficiency will be $\eta \times 100=\dfrac{E}{W}\times 100$% = $75$%

Multiple choice physics machines levers and pulleys pulley pulleys

It is easy to draw water from a well when the rope passes over a pulley than drawing it directly. Because :

  1. Pulley adds more force

  2. Pulley decreases the weight of the bucket

  3. Pulley has a mechanical advantage of more than one

  4. Pulley changes the direction of force
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A single fixed pulley does not provide a mechanical advantage greater than one, nor does it reduce the weight of the load. Its primary purpose and advantage in this context is changing the direction of the applied force, making it more convenient to pull downward.