# Hoppers Physics

Revision tips and links for common entrance and ks3 physics

## Tuesday, October 25, 2016

### Pupil packs

Don't miss our pupil packs, tests, experiments and worksheets on tes resources each one covers a part of the common entrance and ks 3 syllabus and features experiments, graduated differentiation and plenty of other science skills as well as problem solving tasks visit our shop today 25% many resources now

## Saturday, February 20, 2016

### Our videos

And don't forget to visit our shop at tes resources

## Tuesday, February 16, 2016

### Light:reflection

**Scattering**

**The law of reflection**

## Sunday, February 14, 2016

### Light : Basics

Remember light travels in straight lines (unless it goes past a star or black hole when they can be bent). In space light travels at 300,000,000 m/s around a million times faster than sound travels through the air. Luminous objects are light sources they give out light. Materials can be described as

**transparent**(let's through all the light),

**translucent**(let's through some light) or

**opaque**(let's through no light). Remember the thickness of the material is important! One sheet of paper is translucent but 100 sheets will be opaque. We also need to know about reflection, refraction and dispersion which are coming in the next post.

## Tuesday, February 9, 2016

### Speed

Speed measures how far we travel in a unit of time. This is why we measure it in miles per hour. Miles measure distance per means in every and hours measure time. Of course there are other units of speed as well such as kilometres per hour and meters per second which we use a great deal in common entrance physics. Fast and slow moving things might need different units. A rocket will move a certain number of kilometres per second (around 11 km/s to escape earth orbit) a glacier might move a few

centimetres/year. It would be silly to measure these movements in meters per second the numbers would be really big or really small and any calculations you do complicated.

So to measure speed we need to know the distance moved and the time taken. Then we divide the distance by the time. In other words:

Speed= distance / time

If you forget this just think of a speed you go in your car. 50 miles per hour. Miles (distance) per (divided by) hours (time).

I am on a train as I write this we are going 60 miles in 2 hours so the speed is

S=d/t

S=60/2=30 mph

Remember this will be our average speed. We stop at each station, speed up and slow down all the way so we won't go at 30mph exactly much of the time.

If my train was travelling for 4 hours at this average speed how far would it go?

Well the distance=speed x time

Distance =30 x 4 =120 miles.

This is because the speed tells us the distance we go each hour if I go 4 lots of 30 that is 120 miles.

So how long would it take my train to do 105 miles?

Here we do time=distance/speed

Time=105/30=3.5 hours.

Take care. Exam question setters love to put in traps. Look at this question.

A horse travels at 8m/s for two minutes how far does it go?

Here I have muddled up minutes and seconds. The first thing we must work out is how many seconds the horse is travelling for. 2x60=120 (as there are 60 seconds in one minute)

Now we can do

distance=speed x time

Distance=8 x120

Distance=960m