Multiple choice As Physics AQA question Help needed.

A car exerts a driving force of 500N when travelling at a constant speed of 72 KMH-1 on a level track. What is the work done in 5 minutes??

According to the marksceme the answer is 2.0x10^5

Can someone explain how to get that that answer. Thanks !

Reply 1

Teenie2

I don't get that answer, what I get is :-

Work done = Force * Distance.

Distance travelled = speed * time = 72 * (5/60) = 6km = 6000m

So, Work done - 500N * 6000m = 3x10^6 Nm

Is that what you've been getting?

Reply 2

Joinedup

72 km h^-1 = 20 m s^-1

in 300 secs the car travels 6000 m

over that distance the car is exerting constant 500N force

work done = Fs

500 x 6000 = 3x10^6 J

Reply 3

srata

72KmH-1 = 20m/s

P=FV
20*500= 10,000W
PT=E
(5mins= 300 secs)
10,000*300= 3x10^6J

Reply 4

Joinedup

fwiw MS says 3.0 x 10^6 J too

Q23 in paper http://filestore.aqa.org.uk/resources/physics/AQA-74081-SQP.PDF#24

answer to 23 is A (3.0 x 10^6 J)
in MS http://filestore.aqa.org.uk/resources/physics/AQA-74081-SMS.PDF#13

Reply 5

Teenie2

I think you've been reading the wrong bit of the mark scheme Kraixo - the answer is A - 3x10^6J

Reply 6

username3295148

The mark scheme states that it is C 2.0*10^6 but when calculated it comes to 3.0*10^6 (A)

Reply 7

Pangol

When this specimen paper was first released, there were a couple of errors on the mark scheme, including this one. As others have pointed out, they have since put it right!

Reply 8

username3295148

I got this question from physics and maths tutor

Reply 9

Pangol

Original post by MH1234567

I got this question from physics and maths tutor

Very useful though that site is, the questions and marks schemes are largely just those from the exam boards. He has presumably put up the mark scheme that was released with the paper originally, rather than the corrected version.

Reply 10

Yungkillag

Original post by username1894983

Distance = speed x time. Speed is in m/s so it is 72 x 10^3 / 3600. Now multiply that by 300 seconds which is the 5 minutes. Now W=fd (one of the few equations not given in formula sheet) so do 500 x the distance u got thats how its done