178865
Badges: 6
Rep:
?
#1
Report Thread starter 2 years ago
#1
This question is from set 2 paper 1 of the AQA AS physics specimen materials:

A car is designed to break the land speed record. The thrust exerted on the car is 230 kN at one instant of its motion. The mass of the car at this instant is 11 000 kg.
The acceleration of the car at this instant is 2.9 m s–2 .
Calculate the air resistance acting on the car.

I would have calculated the resultant force from acceleration * mass, and taken this away from the thrust, which would have given me 198100N, but this is not correct according to the mark scheme.


The mark scheme says:

resultant force = 245 000 × 2.9 = 710 500 (N)
resultant force = thrust – weight – air resistance 710 500 = (3200 × 103 – 245 × 103 ) × 9.81 – air resistance
air resistance = (3200 × 103 – 245 × 103 ) × 9.81 – 710 500 = 86 000 (N)

I don't understand where the 245000 comes from on the first line of the MS, or where the weight comes into it. Am I missing a formula or something?
0
reply
Presto
Badges: 17
Rep:
?
#2
Report 2 years ago
#2
Bump
0
reply
178865
Badges: 6
Rep:
?
#3
Report Thread starter 2 years ago
#3
I suspect it's a bogus question, but it's from AQA's official specimen material, so I'm not sure.
0
reply
assassinjeev22
Badges: 14
Rep:
?
#4
Report 2 years ago
#4
(Original post by 178865)
This question is from set 2 paper 1 of the AQA AS physics specimen materials:

A car is designed to break the land speed record. The thrust exerted on the car is 230 kN at one instant of its motion. The mass of the car at this instant is 11 000 kg.
The acceleration of the car at this instant is 2.9 m s–2 .
Calculate the air resistance acting on the car.

I would have calculated the resultant force from acceleration * mass, and taken this away from the thrust, which would have given me 198100N, but this is not correct according to the mark scheme.


The mark scheme says:

resultant force = 245 000 × 2.9 = 710 500 (N)
resultant force = thrust – weight – air resistance 710 500 = (3200 × 103 – 245 × 103 ) × 9.81 – air resistance
air resistance = (3200 × 103 – 245 × 103 ) × 9.81 – 710 500 = 86 000 (N)

I don't understand where the 245000 comes from on the first line of the MS, or where the weight comes into it. Am I missing a formula or something?
No, your working is right. Thats the thing with these specimen papers some of the answers are wrong.
0
reply
Eimmanuel
Badges: 13
Rep:
?
#5
Report 2 years ago
#5
(Original post by 178865)
This question is from set 2 paper 1 of the AQA AS physics specimen materials:

A car is designed to break the land speed record. The thrust exerted on the car is 230 kN at one instant of its motion. The mass of the car at this instant is 11 000 kg.
The acceleration of the car at this instant is 2.9 m s–2 .
Calculate the air resistance acting on the car.

I would have calculated the resultant force from acceleration * mass, and taken this away from the thrust, which would have given me 198100N, but this is not correct according to the mark scheme.


The mark scheme says:

resultant force = 245 000 × 2.9 = 710 500 (N)
resultant force = thrust – weight – air resistance 710 500 = (3200 × 103 – 245 × 103 ) × 9.81 – air resistance
air resistance = (3200 × 103 – 245 × 103 ) × 9.81 – 710 500 = 86 000 (N)

I don't understand where the 245000 comes from on the first line of the MS, or where the weight comes into it. Am I missing a formula or something?
Someone in the forum actually commented it is about a rocket NOT car problem for this set of paper. You can find the comment here.
https://www.thestudentroom.co.uk/sho...3968699&page=4
1
reply
178865
Badges: 6
Rep:
?
#6
Report Thread starter 2 years ago
#6
Thank you everyone.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

How are you feeling ahead of starting University?

I am excited and looking forward to starting (59)
13.41%
I am excited but have some apprehension around Covid-19 measures (57)
12.95%
I am concerned I will miss out on aspects of the uni experience due to new measures (168)
38.18%
I am concerned the Covid-19 measures at uni are not strong enough (46)
10.45%
I am nervous and feel I don't have enough information (87)
19.77%
Something else (let us know in the thread!) (23)
5.23%

Watched Threads

View All