S3 Revsion

Forces – Worked Example Forces acting on a beam worked example

100N

3m 2m

R1

P

Moment = Force x Distance

100N x 5m = 500Nm

Force R1 = Moment / Distance= 500Nm/2m

R1 = 250N

Forces Problems500KN

10m 2m

R1

P1000N

1m 5m

R1

P

20KN

6m 4m

R1

P

Voltage Divider – Worked example

5V

0V

5k

2k

Vout

Vout = R1/Rt x Vs

Vout = 5000 / 7000 x 5

Vout= 3.5v

Voltage Dividers examples

5V

0V

7k

3k

Vout

9V

0V

15k

20k

Vout

12V

0V

5k

5k

Vout

Calculating Total Resistance20

2

6

Calculate the total resistanceStep 1 calculate the total resistance in parallel

1/RT = 1/R1+1/R2

1/RT = 2/12 + 6/121/RT = 8/12 OR 12/8 RT = 1.5 OHMS

Total resistance is:

RT = 20 + 1.5

Total resistance is 21.5 ohms

Calculating Total Resistance20

10

20

50

120

30

5k

15

60

Heat Energy Calculate the heat energy of 5 litres of water in a kettle which has had its temperature raised from 20°c to 80°C (I litre of water a mass 1kg) Specific heat capacity of water is 4200

Eh= mc Δ T Eh = 5 x 4200 x 60 Eh = 1260000 J

Heat Energy 1. Calculate the heat energy of 10 litres of water in a kettle which has had its temperature raised from 40°c to 80°C (I litre of water a mass 1kg) Specific heat capacity of water is 4200

2. Calculate the heat energy of 2 litres of water in a kettle which has had its temperature raised from 40°c to 42°C (I litre of water a mass 1kg) Specific heat capacity of water is 4200

3. Calculate the heat energy of 15 litres of water in a kettle which has had its temperature raised from 60°c to 100°C (I litre of water a mass 1kg) Specific heat capacity of water is 4200

Mechanisms