Hey! Sign in to get help with your study questionsNew here? Join for free to post

Mechanics Help

Announcements Posted on
TSR's new app is coming! Sign up here to try it first >> 17-10-2016
    • Thread Starter

    A particle of mass 0.5 kg is held at rest at a point P, which is at the bottom of an inclined plane. The particleis given an impulse of 1.8 N s directed up a line of greatest slope of the plane. (i) Find the speed at which the particle starts to move.

    The particle subsequently moves up the plane to a point Q, which is 0.3 m above the level of P. (ii) Given that the plane is smooth, find the speed of the particle at Q.
    The initial velocity is 3.6ms. I found the answer to question 2 by subtracting the mgh from the initial K, as such: 1/2mv^2 = 1/2mu^2 - mgh; and solving for v. V= 2.66 ms.
    I do not understand how I got this answer, because the particle is travelling up the slope so should be losing KE and gaining PE, so it makes more sense to me to subtract the KE instead of the PE. I would really appreciate some help. Thanks in advance.

    Hi I'm not doing mechanics 2 but thought I would have a look. The ball is moving up the slope with a given kinetic energy, which at point Q the initial kinetic energy supplied to the ball will be reduced and the gravitational potential will be increased (conservation of energy).
    Therefore kinetic energy before, which I worked out to be 1/2*0.5*3.6^2 = 3.24J is equal to the sum of the final gravitational potential energy (mgh) and the final kinetic energy.

    3.24 = 1/2*m*v(final)^2 + mgh
    therefore v(final) = 2.66m/s
Write a reply…


Submit reply


Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. Oops, you need to agree to our Ts&Cs to register
  2. Slide to join now Processing…

Updated: May 14, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

Do you like sleeping in a cold room?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.