Forces and motion
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Define force and state its units. 2 marks
A force is a push or pull on an object. It is measured in Newtons (N).
A force can make an object do what? 2 marks
• Forces can set a still object into motion. • Forces can change a moving object’s speed and velocity.
Distinguish between a balanced and unbalanced force. What do they look like on a force diagram? 4 marks
A balanced force is when two opposite forces are the same size. An unbalanced force is when one force is bigger than its opposite. In a force diagram, a balanced force will have two opposing arrows of the same size, but and unbalanced force will have one arrow that is bigger than the other.
Define friction and give examples. 4 marks
Friction is a force which opposes the relative motion of two contact areas. Examples include: * rubbing your hands together * applying the brakes to a moving vehicle * sliding down a slide
What is lubricant and how is it used in relation to friction? 2 marks
Lubricant is a substance that helps to reduce friction between surfaces. It is often used in machinery to reduce friction between moving parts.
State advantages and disadvantages to friction. 4 marks
Advantages * It is used in brakes * It is used to light matches Disadvantages * It can wear down moving parts in machinery * It produces a lot of energy, released mostly as heat and sound
Define air resistance and give an example. 2 marks
Air resistance is a resistive force that acts against objects that are moving through the air. An example is a parachute.
Define terminal velocity. 1 mark
Terminal velocity is the constant speed that a freely falling object reaches when air resistance prevents further acceleration.
State the law of the lever. 1 mark
Effort times effort arm equals load times load arm.
Define the fulcrum and the load. 2 marks
The fulcrum is the pivot of a lever, and the load is the stuff being lifted by the lever.
What is the unit for a turning force and what is the equation for it? 2 marks
Moments (measured in Nm) Moment (Nm) = Force (N) x Distance (m)
State the law of moments. 1 mark
The law of moments states that when a body is balanced, the total clockwise moment about a point equals the total anticlockwise moment about the same point.
State Hooke’s Law. 1 mark
Hooke’s Law states that the extension of the elastic material is directly proportional to the force applied, provided the elastic limit has not been exceeded.
Describe an experiment to demonstrate Hooke’s Law. 8 marks
Apparatus (2) * Clamp and clamp stand * Spring * Metre ruler * 100g masses Method (4) * Set up the apparatus with the spring hanging from the clamp. * Measure the length of the spring with no load. * Add a 100g mass (1N) and record the length of the spring. * Continue to add 100g and measure the length of the spring each time. Record these results in a graph. The graph should have a straight line of best fit until the elastic limit has been exceeded, at which point it will curve. (2)