Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta

M1 mechanics -constant acceleration hwk help watch

    • Thread Starter
    Offline

    17
    ReputationRep:
    Hi,

    Please could I have some help with these mechanics questions, I am very stuck. For the 1st question I tried to create and solve a simultaneous equation connecting the 2 heights and using T and T+3 for the times of the 2 balls being thrown however I've come out with T being 40 and therefore using S=ut+1/2at^2 a displacement of -7000 which I feel is very wrong!

    Thanks
    Attached Images
     
    • Very Important Poster
    Online

    21
    ReputationRep:
    Very Important Poster
    (Original post by VioletPhillippo)
    Hi,

    Please could I have some help with these mechanics questions, I am very stuck. For the 1st question I tried to create and solve a simultaneous equation connecting the 2 heights and using T and T+3 for the times of the 2 balls being thrown however I've come out with T being 40 and therefore using S=ut+1/2at^2 a displacement of -7000 which I feel is very wrong!

    Thanks
    Remember that you've defined T as the length of time that B is in the air - it will be important in the question.

    What were the simultaneous equations that you made, and how did you solve them?
    • Thread Starter
    Offline

    17
    ReputationRep:
    (Original post by SeanFM)
    Remember that you've defined T as the length of time that B is in the air - it will be important in the question.

    What were the simultaneous equations that you made, and how did you solve them?
    Thanks, I've just done question 1 again by equating the equations 25T-5T^2= 25(T-3)-5(T-3)^2 and time came out to be 4 with a displacement of 20(I'm not sure if this is correct but it seems more realistic) for part ii. I realised that the 1st time I accidentally did 120/30 = 40 rather than 4.I'm still stuck with question 2 though
    • Very Important Poster
    Online

    21
    ReputationRep:
    Very Important Poster
    (Original post by VioletPhillippo)
    Thanks, I've just done question 1 again by equating the equations 25T-5T^2= 25(T-3)-5(T-3)^2 and time came out to be 4 with a displacement of 20(I'm not sure if this is correct but it seems more realistic) for part ii. I realised that the 1st time I accidentally did 120/30 = 40 rather than 4.I'm still stuck with question 2 though
    Nice, well done and since you're using T and T - 3 you've defined T as the time A is in the air so you've already got the answer of 4s

    For the two time periods, it may help to write out 'S U V A T' and write out what information you've been given, if any, under each letter, and if you don't know them then assign something to them, like for the first one v = v1.
    • Thread Starter
    Offline

    17
    ReputationRep:
    Thanks for your help. I've got T=4 so then T-3=1. Then for part ii. I've subbed T=4 into S=uv+1/2at^2 to get displacement as 20m. Is this the right way?

    Also I'm stuck on how to do question 2 about the train as I'm not really sure what the best approach is.
    • Very Important Poster
    Online

    21
    ReputationRep:
    Very Important Poster
    (Original post by VioletPhillippo)
    Thanks for your help. I've got T=4 so then T-3=1. Then for part ii. I've subbed T=4 into S=uv+1/2at^2 to get displacement as 20m. Is this the right way?

    Also I'm stuck on how to do question 2 about the train as I'm not really sure what the best approach is.
    Woops :facepalm: I gave you a hint for q2 instead of part ii) of question 1, sorry!

    And yes, that's fine for part ii)

    See my previous post for a hint on q2.
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: November 12, 2015
Poll
Do you agree with the proposed ban on plastic straws and cotton buds?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

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

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