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# forces - PowerPoint PPT Presentation

forces. Define forces as pushes or pulls which can cause objects to ; speed up, slow down, change direction. forces. Force: the general name for a push, pull or twist (torque). Forces can start, stop or change the direction in the movement of an object.

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## PowerPoint Slideshow about 'forces' - colt-daniels

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Presentation Transcript

### forces

Define forces as pushes or pulls which can cause objects to ; speed up, slow down, change direction

forces
• Force: the general name for a push, pull or twist (torque).
• Forces can start, stop or change the direction in the movement of an object.
• Forces can change the shape of an object.
• When changes take place, there is a transformation of energy.
• Stick in the handout and have a go at the task.
F=ma
• Force = mass X acceleration
• Force (F) is measured in Newtons (N)
• Mass (m) is measured in kilograms (kg)
• Acceleration (a) is measured in metres per second per second (ms-2 )
Contact vs non-contact
• Some forces occur when contact is made. E.g. pushing a trolley.
• Some forces occur without any contact being made. E.g. gravity is a pulling force. Magnets can push or pull without touching an object
Gravity:
• Gravity is the force that keeps us on the Earth.
• It pulls all objects down.
• F = ma: W=mg: these formulas are “the same”
• Weight (W) is the measure of the force of gravity and is measured in Newtons (N)
• Mass (m) is measured in kilograms (kg)
• Gravity (g) is measured in metres per second per second and has a fixed value of 10. i.e. 10 ms-2
• What is your weight on Earth if your mass is 60kg?
• W=mg;
• W= 60 X 10
• = 600N
Weight vs mass
• the mass is how much of something there is. It doesn’t change. If there is 10kg of something, there will still be 10kg of something in space or on the moon.
• The weight of something is how “heavy” it is. It changes depending on the gravity. In space the object would be weightless (as there is no gravity), on the moon an object would have a weight 1/6th of that on Earth as the gravitational pull on the moon is less than Earth.
• E.g. mass on Earth = 60kg, weight on Earth = 600N;

mass on moon = 60 kg, weight on moon = 600/6=100N

mass in space = 60 kg; weight in space = 60kg X 0 = 0N

Problems:
• In your own words, describe what force is.
• Give 3 examples of forces in action.
• Explain whether a force will always cause movement
• Explain how forces affect our every day lives
• Stick in the pictures and list the types of forces shown in each
• Stick in the experiment and complete it.