Newton second law and pendulum

A pendulum is hanged in the car.
Car starts to move by constant acceleration
How to measure acceleration by angle the pendulum?

Asked Afshin



If the pendulum makes an angle θ with the vertical, then a = g tan θ

This is based on the idea of pseudo force experienced by a body in an accelerated frame of reference.

When a body is in an accelerated frame of reference, it feels as if it is acted upon by a force equal to its mass multiplied by the acceleration of the system. Please have a look at the diagram below.


Please feel free to ask further doubts on the topic via comments

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question from calorimetry

​I just did an experiment and now we need to find out the mass of ice we used.

Initial temperature is 55 degrees
Final temperature is 35 degrees
we were given 3 information which was the Heat capacity of a calorimeter = 80JC^-1
Specific heat capacity of water = 4.2×10^3Jkg^-1
Specific latent heat of ice which was 3.4×10^5Jkg^-1

I dont know how to work it out can you help meAsked Thilaksan

You have to apply the principle of calorimetry

Heat lost =Heat lost

Heat liberated by cooling water & calorimeter  from 55 to 35 = Heat gained by ice to melt + heat gained by water(produced by the melting of ice) from 0 to 35

Note you may make a try. Further assistance can be provided if required

Find the kicking force

A football player kicks a 0.5kg ball and imparts it a velocity of 10m/s . The contact between foot and ball is for 1 /50th second. Find the kicking force

Problem from magnetism

एक लघु चुम्बक को चुम्बकीय याम्योतर में इस प्रकार रखा जाता है कि उसका दक्षिणी धु्व उत्तर की ओर रहता है।चुम्बक के केन्द् से 20cm की दुरी पर उदासीन बिन्दु प्राप्त होता है। यदि उस बिन्दु पर भु-चुम्बकिय क्षैतिज घटक का मान 0•3gause है तो चुम्बक का चुम्बकिय आघुण्र होगा।


Resultant Force

One of two rectangular components of force is 5N and it makesan angle of 60 with the force the magitude of the force is?
the answer is 10N but how? explain

Asked Iqra

Problem from ray optics

A Ray of light is incident at 50 degrees on the middle of one of the two Mirrors arranged at an angle of 60 degrees between them the Ray then touches the second mirror get reflected back to the first mirror making an angle of incidence of ?

Posted by Prathisha