Forces

• Scalar quantities have magnitude only. Vector quantities have magnitude and an associated direction. A vector quantity may be represented by an arrow. The length of the arrow represents the magnitude, and the direction of the arrow the direction of the vector quantity.
• A force is a push or pull that acts on an object due to the interaction with another object. All forces between objects are either: • contact forces – the objects are physically touching • non-contact forces – the objects are physically separated. Examples of contact forces include friction, air resistance, tension and normal contact force. Examples of non-contact forces are gravitational force, electrostatic force and magnetic force. Force is a vector quantity.
• A force is a push or pull that acts on an object due to the interaction with another object. All forces between objects are either: • contact forces – the objects are physically touching • non-contact forces – the objects are physically separated. Examples of contact forces include friction, air resistance, tension and normal contact force. Examples of non-contact forces are gravitational force, electrostatic force and magnetic force. Force is a vector quantity.
• describe the interaction between a baseball bat and a baseball.

  The baseball forces the bat to the left; the bat forces the ball to the right. Together, these two forces exerted upon two different objects form the action-reaction force pair.
• Weight is the force acting on an object due to gravity. The force of gravity close to the Earth is due to the gravitational field around the Earth. The weight of an object depends on the gravitational field strength at the point where the object is.
• weight, W, in newtons, N mass, m, in kilograms, kg gravitational field strength, g, in newtons per kilogram, N/kg (In any calculation the value of the gravitational field strength (g) will be given.) The weight of an object may be considered to act at a single point referred to as the object’s ‘centre of mass’.
• The weight of an object and the mass of an object are directly proportional. Weight is measured using a calibrated spring-balance (a newtonmeter)
• A number of forces acting on an object may be replaced by a single force that has the same effect as all the original forces acting together. This single force is called the resultant force
• describe examples of the forces acting on an isolated object or system

  Every force acting on object or system, has none of the forces exerted to the rest of the world
• When a force causes an object to move through a distance work is done on the object. So a force does work on an object when the force causes a displacement of the object.
• work done, W, in joules, J force, F, in newtons, N distance, s, in metres
• One joule of work is done when a force of one newton causes a displacement of one metre. 1 joule = 1 newton-metre
• describe the energy transfer involved when work is done

  Work done involves transferring energy, so we need the energy to come from somewhere before we transfer it. For example, if a person pushes a wheelbarrow, chemical energy is converted to kinetic energy to move the wheelbarrow. The chemical energy originates from the food the person eats.
• Work done against the frictional forces acting on an object causes a rise in the temperature of the object.
• give examples of the forces involved in stretching, bending or compressing an object

  if you just pushed a spring, then it would move in a certain direction. But if you pushed both ends of the spring, the spring would compress.
• give examples of the forces involved in stretching, bending or compressing an object

  if you just pushed a spring, then it would move in a certain direction. But if you pushed both ends of the spring, the spring would compress.
• explain why, to change the shape of an object (by stretching, bending or compressing), more than one force has to be applied

  a single force would simply cause the object to move in the direction in which the force were to be applied
• explain why, to change the shape of an object (by stretching, bending or compressing), more than one force has to be applied

  a single force would simply cause the object to move in the direction in which the force were to be applied
• describe the difference between elastic deformation and inelastic deformation caused by stretching forces

  The elastic limit of a material is the furthest amount it can be stretched or deformed without being able to return to its previous shape. Once a material has gone past its elastic limit, its deformation is said to be inelastic. The higher the spring constant, the stiffer the spring.
• The extension of an elastic object, such as a spring, is directly proportional to the force applied, provided that the limit of proportionality is not exceeded.
• force, F, in newtons, N spring constant, k, in newtons per metre, N/m extension, e, in metres, m
• This relationship also applies to the compression of an elastic object, where ‘e’ would be the compression of the object. A force that stretches (or compresses) a spring does work and elastic potential energy is stored in the spring. Provided the spring is not inelastically deformed, the work done on the spring and the elastic potential energy stored are equal.
• describe the difference between a linear and non-linear relationship between force and extension

  If an object doesn't obey Hooke's law, there is a non-linear relationship between force and extension.if it does there is a linear relationship
• Secure a clamp stand to the bench using a G-clamp or a large mass on the base
• Use bosses to attach two clamps to the clamp stand
• Attach the spring to the top clamp, and a ruler to the bottom clamp
• Adjust the ruler so that it is vertical, and with its zero level with the top of the spring
• Measure and record the unloaded length of the spring
• Hang a 100 g slotted mass carrier - weight 0.98 newtons (N) - from the spring
• Measure and record the new length of the spring
• Add a 100 g slotted mass to the carrier
• Repeat adding a 100 g slotted mass to the carrier and measuring the new length of the spring until a total of 1,000 g has been added
• Distance is how far an object moves. Distance does not involve direction. Distance is a scalar quantity. Displacement includes both the distance an object moves, measured in a straight line from the start point to the finish point and the direction of that straight line. Displacement is a vector quantity
• Distance is how far an object moves. Distance does not involve direction. Distance is a scalar quantity. Displacement includes both the distance an object moves, measured in a straight line from the start point to the finish point and the direction of that straight line. Displacement is a vector quantity
• express a displacement in terms of both the magnitude and direction.

  The magnitude (or length) of the displacement vector is the distance between the points and is represented by the length of the arrow. The direction of the displacement vector is the direction of the arrow.
• Speed does not involve direction. Speed is a scalar quantity. The speed of a moving object is rarely constant. When people walk, run or travel in a car their speed is constantly changing. The speed at which a person can walk, run or cycle depends on many factors including: age, terrain, fitness and distance travelled
• walking ̴ 1.5 m/s running ̴ 3 m/s cycling ̴ 6 m/s
• walking ̴ 1.5 m/s running ̴ 3 m/s cycling ̴ 6 m/s
• It is not only moving objects that have varying speed. The speed of sound and the speed of the wind also vary. A typical value for the speed of sound in air is 330 m/s
• distance, s, in metres, m speed, v, in metres per second, m/s time, t, in seconds,