Join TSR now and get all your revision questions answeredSign up now
    • Thread Starter
    Offline

    0
    ReputationRep:
    Two vehicles travelling on a road in the same direction collide. Vehicle 1 has a mass 1200 kg and is travelling at 30m/s. Vehicle 2 has a mass 900 kg and is travelling at 45m/s. Assuming that the cars momentarily lock together and continue moving in the same direction determine the new velocity (combined) of the cars after the collision.

    for this i have the answer of 36.4286m/s

    assuming that is correct the question im stuck on is this

    c)If the time of deceleration of vehicle 2 during the collision is 0.15 seconds determine the average force acting on this vehicle during this time.

    my answer is this

    force = mass x deceleration

    deceleration = (45 - 36.4286) / 0.15 = 57.143

    therefore force = 900 x 57.143 = 51428.7N ?????? IS THIS COMPLETELY WRONG ???

    help much appreciated
    Offline

    0
    ReputationRep:
    (Original post by lauren088)
    Two vehicles travelling on a road in the same direction collide. Vehicle 1 has a mass 1200 kg and is travelling at 30m/s. Vehicle 2 has a mass 900 kg and is travelling at 45m/s. Assuming that the cars momentarily lock together and continue moving in the same direction determine the new velocity (combined) of the cars after the collision.

    for this i have the answer of 36.4286m/s

    assuming that is correct the question im stuck on is this

    c)If the time of deceleration of vehicle 2 during the collision is 0.15 seconds determine the average force acting on this vehicle during this time.

    my answer is this

    force = mass x deceleration

    deceleration = (45 - 36.4286) / 0.15 = 57.143

    therefore force = 900 x 57.143 = 51428.7N ?????? IS THIS COMPLETELY WRONG ???

    help much appreciated
    Draw two diagrams of the before and after collision with the initial velocity and final velocity, make sure if the car changes direction you appreciate the fact that if taking -> to be positive then <- would be negative. Use the conservation of momentum M_1U_1+M_2U_2=M_1V_1+M_2V_2 to determine the missing variable
    Hint V_1=V_2 as there is a combined value of velocity, so you can just name the variable V for both parts
    You really need to show us the working to help you with each part
    Offline

    2
    ReputationRep:
    (Original post by lauren088)
    Two vehicles travelling on a road in the same direction collide. Vehicle 1 has a mass 1200 kg and is travelling at 30m/s. Vehicle 2 has a mass 900 kg and is travelling at 45m/s. Assuming that the cars momentarily lock together and continue moving in the same direction determine the new velocity (combined) of the cars after the collision.

    for this i have the answer of 36.4286m/s

    assuming that is correct the question im stuck on is this

    c)If the time of deceleration of vehicle 2 during the collision is 0.15 seconds determine the average force acting on this vehicle during this time.

    my answer is this

    force = mass x deceleration

    deceleration = (45 - 36.4286) / 0.15 = 57.143

    therefore force = 900 x 57.143 = 51428.7N ?????? IS THIS COMPLETELY WRONG ???

    help much appreciated
    It seems to be correct to me. Although the bit in bold should technically be (36.43-45)/0.15 to give you an acceleration of -57.1 m.s^-2 which is a deceleration of 57.1 m.s^-2 (remember a=(v-u)/t. But other than that, it all seems fine.

    I would also leave the final answer to 3 significant figures so for the above F=51,400N
 
 
 
Poll
If you won £30,000, which of these would you spend it on?
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

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