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GCSE: Forces and Motion
Set aside a few hours every week to re-read old notes, play revision games, make mind maps etc. Find what works for you.
723 GCSE Forces and Motion essays
- Marked by Teachers essays 5
- Peer Reviewed essays 15
*** An interesting report but there are some concerns over the validity of the results.
Planning. There needed to have been much more thought put in regarding the control of…
- Essay length: 1643 words
- Submitted: 24/12/2006
- Marked by teacher: Stephanie Wells 01/03/2013
Overall a 3 star piece of work. The practical procedure should yield some valid data. It is a method that could be followed by other people. The conclusion could be…
- Essay length: 547 words
- Submitted: 28/08/2003
- Marked by teacher: Brady Smith 13/03/2013
The writer has gone into great detail in order to answer the question, and as a result produced a brilliant and well written report. It was good for the writer…
- Essay length: 3683 words
- Submitted: 26/06/2009
- Reviewed by: cpdavis 01/03/2012
The student answers the question well, he at first explains the theory then makes predictions based on theory. I would recommend this as you get your marks for explaining why…
- Essay length: 2341 words
- Submitted: 27/10/2007
- Reviewed by: jackhli 28/02/2012
Aim To investigate the effect of different masses suspended from a spring on the time period of the spring.3 star(s)
A topic which is beyond the scope of the GCSE syllabus was experimented by the author. It most definitely answered the question to a certain extent, however lack of further…
Balanced and unbalanced forces
- 1 There are many words which mean force. E.g. push, pull, friction, weight, air resistance, tension, thrust. All are measured in newtons (N).
- 2 When a body is acted on by more than one force at the same time, the overall force is called the resultant force. E.g. if a car is pushed to the right with a force of 500 N and to the left with a force of 200 N, the resultant force is 300 N.
- 3 When the resultant force is greater than zero, the forces are unbalanced and this will cause a change in speed or direction, or both. For the example of the car, the 200 N resultant force would cause the car’s speed to increase so the car is accelerating.
- 4 What if the brakes are applied to the car? The braking force acts in the opposite way to the direction in which the car is moving. This time the speed decreases and the car is decelerating.
- 5 When the resultant force is zero, the forces are balanced. The body will continue to move with a constant speed in the same direction. This is true for a skydiver falling with a constant speed called the terminal speed. The air resistance is equal to the weight.
- 1 When the forces on a body are unbalanced, the resultant force, F causes an acceleration, a. We can calculate the acceleration using an equation F = ma.
- 2 In this equation m is the mass of the body measured in kilograms (kg). F is the force measured in newtons (N) and a is the acceleration measured in m/s2.
You should practice how to write the equation in three different ways by rearranging it:
1) F = ma
2) m = F/a
3) a = F/m
- 4 Suppose a resultant force of 20 N acts on a body giving it an acceleration of 4 m/s2. What is the mass of the body? Choose an equation for m, so we use m=F/a = 20/4 = 5N.
- 5 A car of mass 2000 kg is acted on by a force of 500 N. What is the acceleration? Choose the equation for a, so we use a = F/m = 500/2000 = 0.25 m/s2.
Motion under gravity
- 1 The weight of a body, W is a force and it can be calculated from the equation W=mg. g is the gravitational field strength. On Earth, g has a value of 9.81 N/kg.
- 2 What is the weight of a mass of 20 kg? W = mg = 20 x 9.81 = 196.2 N
- 3 On the Moon, the value of g is much smaller than on Earth , so the same body will have a smaller weight . The value of g on the Moon is about one sixth of g on Earth so the weight will be ⅙ of the weight on Earth. So the mass of a body doesn’t change when the body is moved from the Earth to the Moon but its weight changes.
- 4 If weight is the only force acting on a body, then we can use the weight to calculate the acceleration when a body is released. What is the acceleration of an apple of mass 0.1 kg which falls from a tree? W = mg = 0.1 x 9.81 = 0.981 N. Now we can calculate the acceleration using a = F/m. (Remember that F=W) so a = 0.981/0.1 = 9.81 m/s2.
- 5 Even if we had changed the mass of the apple to 0.2 kg, the acceleration would still be the same! The apples would hit the ground at the same time.
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