AQA AS Physics C10 Work,Energy And Power Kerboodle Answers

Banner 1

C10.1 Work and energy AQA AS Physics C10 WorK,Energy And Power Kerboodle Answers: Page No. 172

1.Ans-
a) a weight of 40 N is raised by a height of 5.0m
200J
b a spring is stretched to an extension of m by a force that increases to 20 N.
4.5J
2.Ans-
a in the direction of the force
48 J
b in a direction at to the direction of the force
24J
c in a direction at right angles to the direction of the force.
0
3.Ans-
a) the work done pushing the trolley up the slope
1000J
b the gain of potential energy of the trolley
600J
c the energy wasted due to friction.
400J
4.Ans-
a. the force needed to extend it to an extension of 100 mm
2.4N
b the work done when the spring is stretched to an extension of 100 mm from zero extension.
0.12J

10.2 Kinetic energy and potential energy AQA AS Physics C10 WorK,Energy And Power Kerboodle Answers : Page No. 174

1.a its kinetic energy at 6 m
9.0J
b its maximum gain Of potential energy
9.0J
c its maximum height gain.
1.8m
2.
a the loss of potential energy
15.7 kJ
b the gain of kinetic energy Of the cyclist and cycle
5.8 kJ
c the work done against friction and air resistance during the descent
9.9kJ
d the average resistive force during the descent.
20N
3.a its loss of potential energy
590kJ
b its initial kinetic energy
2.4kJ
c its kinetic energy after the descent
470kJ
d the work done against friction
122 kJ
e the average frictional force on it during the descent.
1.6kN

10.3 Power  AQA AS Physics C10 WorK,Energy And Power Kerboodle Answers : Page No. 176

1.
a the gain of potential energy of the student
1.1 kJ
b the useful energy transferred per second.
62.5Js-1
2.
500MW
3. a its gain Of potential energy
156MJ
b its gain Of kinetic energy
140MJ
c the power output of its engine, assuming no energy is wasted due to air resistance.
12MW
4.122m

10.4 Energy and efficiency AQA AS Physics C10 WorK,Energy And Power Kerboodle Answers : Page No. 181

1. a450Js-1
b 1800Js-1
2. a the electrical energy supplied to the motor
480J
b the useful energy transferred by the motor
50J
c the efficiency of the motor.
10%
3.a the energy per second supplied by the fuel
570MJs-1
b the mass of fuel burned per day.
6.2 x 105 kg
4. a) the time taken by the vehicle to travel 1B km at 20 ms-1
600
b the useful energy supplied by the engine in this time
3.7MJ
c the overall efficiency of the engine.
8%

Practice questions: Page No. 182-183

1.(a) Using power = force × speed, top speed

= 1200 W / 600 N
= 20 m s-1
(ii) Distance range = speed × time
= 20 × 90 × 60 m = 108 km
(b)The hybrid car is 1.8 times more fuel efficient than the equivalent petrol-only car.
Its carbon emission would be therefore be 1.8 times less ie. 100 grams per km.
This would cut the annual carbon emission per vehicle by 20000 × 80 grams = 1600 kg or 16 % for the average UK household.
If a significant number of UK motorists switched to hybrid vehicles, there would be significant reduction in UK carbon emissions (eg a 20 % switch would cut UK carbon emissions by 3.2 % (= 20 % of 16 %)).
2.

a) (i) Gravitational potential energy
Changes to kinetic energy
(ii) Both trolley and falling mass gain kinetic energy
Frictional forces cause energy to be converted into thermal energy
(b) Required measurements:
• Masses of the trolley and of the falling mass
• distance (s) fallen by mass and time (t) taken to fall
(c) Relevant points include:
• calculate mgΔh for the falling mass, where Δh = s
• calculate speed of the mass as it hits the floor by using s = ½ (u + v) t, where s and t have been measured and u = 0

3 (a) Use of EP = mgΔh
Gives EP = 1.0 × 9.81 × 4.8 = 47 J
(b)
(c) Relevant points include:
• Locations for power stations are limited (e.g. by geographical and meteorological factors)
• Continuous generation may not be possible (e.g. times of drought)
• Environmental impact (e.g. population is displaced when reservoir is built, damage to wildlife habitats, visual intrusion)
4. (a) The resultant force steadily decreases during the first 4 s
It is zero for the all times beyond 4 s
(b)

Maximum kinetic energy

(c) When at a constant speed, power P = F v
Gives 2.0 × 104 = F × 30
∴ driving force F = 670 N
5 (a) (i) use of ΔEP = m g Δh gives
ΔEP = 70 × 9.81 × 150
= 1.03 × 105 J
(ii)
(b) (i) Work done against air resistance
= (1.03 × 105 ) − (7.09 × 104 )
= 3.21 × 104 J
(ii) Use of work done = F s gives
3.21 × 104 = F × 150
∴ Average resistive force = 210 N (to 2 significant figures)
6.(a) Use of P = F v gives
1.8 × 104 = F × 10 and F = 1800 N
(b)(i) 250 + FR = 1800 gives FR = 1550 N
(ii) New air resistance force = 4 × FR = 6200 N
(iii)Total resistive force
= 6200 + 250 = 6450 N
Use of P = F v gives P = 6450 × 20
= 1.3 × 105 W
7 (a) Relevant points include:
• (gravitational) potential energy is lost (ΔEP)
• Some of this becomes kinetic energy of ball bearing (ΔEK)
• Some is converted into thermal energy (Q)
• Work is done against frictional forces
• ΔEP = ΔEK + Q
(ii) Travels al constant velocity. (6 marks)
Relevant points include:
• Kinetic energy of ball bearing is constant
• Because its speed is constant
• Potential energy lost (ΔEP) is converted into thermal energy (or work done against frictional forces) (Q)
• ΔEP = Q
(b) Potential energy gained by object
= m g Δh = 470 × 9.81 × 0.58 = 2670 J
Work done per stroke of handle
= F s = 150 × 0.42 = 63 J
Total work done = 52 × 63 = 3280 J

= 0.814 (or 81.4 %).

 

DISCLAIMER

Disclaimer: I have tried by level best to provide the answers and video explanations to the best of my knowledge. All the answers and notes are written by me and if there is any similarity in the content then it is purely coincidental. But this is not an alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it. References: BBC Bitesize AQA GCSE Science Kerboodle textbook Wikipedia Wikimedia Commons Join Our Free Facebook Group : Get A* in GCSE and A LEVEL Science and Maths by Mahima Laroyia: https://www.facebook.com/groups/expertguidance.co.uk/ For Free Tips, advice and Maths and Science Help