You are Here: Home >< A-levels

# AS physics

Announcements Posted on
Would YOU be put off a uni with a high crime rate? First 50 to have their say get a £5 Amazon voucher! 27-10-2016
1. A stone of mass 0.4 kg is projected horizontally at a speed of 6.0 m s−1 from the top of a wall, 5.0 m above the surrounding ground. When it arrives at the ground its speed is 10 m s−1. How much energy is lost by the stone in falling through the air?
[1 mark]

A 2.4 J

B 6.8 J

C 12.8 J

D 14.4 J
2. 1/2mv^2 - 1/2mu^2 = Change in KE

Hence, (1/2 x 0.4 x 10^2) - (1/2 x 0.4 x 6^2) = 20 - 7.2 = 12.8J
3. You forgot to take into account the potential energy of the stone.
Initial mechanical energy would be: (0.4)(9.8)(5) + (0.5)(0.4)(36) = 26.8 J;
final mechanical energy would just be the stone's kinetic energy: 0.5(0.4)(100) = 20J

hence delta m.e. is 6.8J

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: May 7, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### University open days

Is it worth going? Find out here

Poll

## All the essentials

### Student life: what to expect

What it's really like going to uni

### Essay expert

Learn to write like a pro with our ultimate essay guide.

### Create a study plan

Get your head around what you need to do and when with the study planner tool.

### Resources by subject

Everything from mind maps to class notes.

### Study tips from A* students

Students who got top grades in their A-levels share their secrets