DD1 is stuck on these questions and I have zilcho knowledge of Physics!!! So anyone who can point us in the right direction would be greatly appreciated!
2 Water waves can be made by vibrating a wooden bar up and down in a tray of water.The bar moves up and down at a frequency of 5 hertz.
(Then diagram showing wave length at 48cm)
2 (a) Calculate the speed, in cm/s, of the water waves.
Write down the equation you use and then show clearly how you work out your answer.
4 (b) Each day the average European family uses 100 kg of hot water.
To kill bacteria, the water going into the tank at 20 °C must be heated to 60 °C.
Calculate the energy needed to increase the temperature of 100 kg of water by 40 °C.
Specific heat capacity of water = 4200 J/kg °C.
Write down the equation you use, and then show clearly how you work out your answer
7 The picture shows a food processor, which is used to grate, shred, liquidise and mix food.
The table gives some information about the food processor.
Energy input Electrical
Useful energy output Kinetic
Power rating 1200 watts
Efficiency 0.8
7 (a) The food processor is used for a total of 30 minutes a day.
Calculate the cost of the energy wasted by the food processor each day.
Electricity costs 15 p per kilowatt-hour.
Write down the equations you use, and then show clearly how you work out your answer.
Thank you very much
Please or to access all these features
Please
or
to access all these features
Connect with other parents whose children are starting secondary school on this forum.
Secondary education
Help Science Teachers (or clever bods!) - Can you tell me how to work out these answers for dd1?
7 replies
Polgara2 · 18/07/2011 08:46
OP posts:
Please create an account
To comment on this thread you need to create a Mumsnet account.