FORCE AND EFFECTS OF FORCES A force is

Weight is a very common force. Weight is the force of gravity due to

If an object is taken on the moon it weights only about one

Sir Isaac Newton, an English scientist, was sitting under an apple tree. An

Forces are measured in units called Newton often written (N) named after Sir

THE DIFFERENCE BETWEEN THE MASS AND THE WEIGHT OF AN OBJECT MASS WEIGHT The

GRAVITY on EARTH Therefore we can say that the Weight of an object is

Friction Friction: Friction is a very common force. When ever on object slides over

Friction can be reduced by: polishing the surfaces; lubricating with oil; separating the surfaces

THE RESULTANT FORCE If two forces act in the same direction, their sum is

THE RESULTANT FORCE Force A If two forces act in opposite direction, their difference

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FORCE AND EFFECTS OF FORCES A force is a push or a pull on an object. Whenever we are pushing or pulling, lifting or bending, twisting or tearing, stretching or squeezing, we are exerting a force. Forces can a) change the speed of an object; b) Change the direction of an object; c)Change the shape of an object

Weight is a very common force. Weight is the force of gravity due to the pull of the Earth, which acts towards the centre of the earth. This force can also be called gravitational attraction.

If an object is taken on the moon it weights only about one sixth (1/6) as much times because the moon is smaller than the Earth and so has less gravitational pull on objects. In the space, objects become weightless.

Sir Isaac Newton, an English scientist, was sitting under an apple tree. An apple from the tree fell down, and hit his head. Then Sir Isaac said: “The force is gravity. ” So he said that the earth pulls objects towards it.

Forces are measured in units called Newton often written (N) named after Sir Isaac Newton. A Newton metre (or Spring balance) is used to measure the weight of an object or to measure the strength of any pulling force. A mass of 1 Kg here on Earth, weighs almost 10 Newtons.

THE DIFFERENCE BETWEEN THE MASS AND THE WEIGHT OF AN OBJECT MASS WEIGHT The mass of an object depends on the number of atoms/molecules (matter) in the object. The weight of an object depends on the pull of gravity on it. The number of atoms/molecules inside an object, NEVER change, so mass never changes. If there is a car of mass 600 kg and we take it on the moon, it’s mass will be 600 kg. A mass of 1 Kg has a weight of 10 N on the earth, because of the gravitational pull. So the same car of 600 Kg has a weight of 6000 N on earth. If we take this car on the moon, its weight will change because the gravity on the moon is not like the gravity of the Earth. In fact, it will weigh less.

GRAVITY on EARTH Therefore we can say that the Weight of an object is equal to the mass of an object multiplied by the constant of gravity (g). The earth pulls an object with a force of 10 N for every 1 kg. (g = 10 N/kg) Weight = Mass x Gravity W = m x g

Friction Friction: Friction is a very common force. When ever on object slides over another object, friction tries to stop the movement. Friction always opposes the movement of an object. (Wheels with ground). Friction can be useful, for example at the brakes and tyres of cars and bicycles. However, it reduces the efficiency of machines, by changing kinetic (movement) energy into heat, which is wasted.

Friction can be reduced by: polishing the surfaces; lubricating with oil; separating the surfaces with air; rolling instead of sliding; streamlining to reduce air resistance.

THE RESULTANT FORCE If two forces act in the same direction, their sum is equivalent to their resultant force. (Force A + Force B) 10 N 5 N = 15 N

THE RESULTANT FORCE Force A If two forces act in opposite direction, their difference is equivalent to their resultant force. (Force A – Force B) 10 N 5 N = 5 N Force B