Forces in action (P2.3) | OCR GCSE Physics A (Gateway Science) — Higher (J249)

P2.3 Forces in action

Summary Forces acting on an object can result in a change of shape or motion. Having looked at the nature of matter, we can now introduce the idea of fields and forces causing changes. This develops the idea that force interactions between objects can take place even if they are not in contact. Learners should be familiar with forces associated with deforming objects, with stretching and compressing (springs). Underlying knowledge and understanding Learners should have an understanding of forces acting to deform objects and to restrict motion. They should already be familiar with Hooke’s Law and the idea that, when work is done by a force, it results in an energy transfer and leads to energy being stored by an object. Learners are expected to know that there is a

force due to gravity and that gravitational field strength differs on other planets and stars. Common misconceptions Learners commonly have difficulty understanding that the weight of an object is not the same as its mass from the everyday use of the term ‘weighing’. The concept of force multipliers can also be challenging even though the basic concepts are ones covered at Key Stage 3.

Reference	Mathematical learning outcomes	Mathematical skills
$PM2.3i$	$force exerted by a spring (N)$

Learning outcomes	To include	Maths	Working scientifically	Practical suggestions
$P2.3a explain that to stretch, bend or compress an object, more than one force has to be applied$	$applications to real life situations$		$WS1.1b, WS1.1e, WS1.2a, WS1.2b, WS1.2c, WS1.2e, WS1.3a, WS1.3c, WS1.3e, WS1.3f, WS1.3g, WS2a, WS2b, WS2c$	$Use of a liquorice bungee or spring to explore extension and stretching. (PAG P2)$
$P2.3b describe the difference between elastic and plastic deformation (distortions) caused by stretching forces$			$WS1.1b, WS1.1e, WS1.2a, WS1.2b, WS1.2c, WS1.2e, WS1.3a, WS1.3c, WS1.3e, WS1.3f, WS1.3g, WS2a, WS2b, WS2c$	$Comparisons of behaviour of springs and elastic bands when loading and unloading with weights. (PAG P2)$
$P2.3c describe the relationship between force and extension for a spring and other simple systems$	$graphical representation of the extension of a spring$	$M1a, M2a, M4a, M4b, M4c$	$WS1.1b, WS1.1e, WS1.2a, WS1.2b, WS1.2c, WS1.2e, WS1.3a, WS1.3c, WS1.3e, WS1.3f, WS1.3g, WS1.4f, WS2a, WS2b, WS2c$	$Investigation of forces on springs - Hooke’s law. (PAG P2)$
$P2.3d describe the difference between linear and non-linear relationships between force and extension$		$M1a, M2a, M4a, M4b, M4c$	$WS1.1b, WS1.1e, WS1.2a, WS1.2b, WS1.2c, WS1.2e, WS1.3a, WS1.3c, WS1.3e, WS1.3f, WS1.3g, WS2a, WS2b, WS2c$	$Investigation of the elastic limit of springs and other materials. (PAG P2)$
$P2.3e calculate a spring constant in linear cases$		$M1a, M2a, M3a, M3b, M3c, M3d$
$P2.3f calculate the work done in stretching$		$M1a, M2a, M3a, M3b, M3c, M3d, M4a, M4b, M4c, M4f$	$WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.2e, WS1.3a, WS1.3c, WS1.3e, WS1.3f, WS1.3g, WS1.4f, WS2c$	$Use of data from stretching an elastic band with weights to plot a graph to calculate the work done. (PAG P2)$
$P2.3g describe that all matter has a gravitational field that causes attraction, and the field strength is much greater for massive objects$
$P2.3h define weight, describe how it is measured and describe the relationship between the weight of an object and the gravitational field strength, g$	$knowledge that the gravitational field strength is known as g and has a value of 10 N/kg at the Earth’s surface$		$WS1.1b$	$Calculations of weight on different planets.$
$P2.3i recall the acceleration in free fall$
$P2.3j ☑ apply formulae relating force, mass and relevant physical constants, including gravitational field strength, g, to explore how changes in these are inter-related$		$M1c, M3b, M3c$
$P2.3k ☑ describe examples in which forces cause rotation$	$location of pivot points and whether a resultant turning force will be in a clockwise or anticlockwise direction$
$P2.3l ☑ define and calculate the moment of a force$	$application of the principle of moments for objects which are balanced$	$M1a, M1c, M2a, M3a, M3b, M3c, M3d$	$WS1.2a, WS1.2b, WS1.3e, WS2a, WS2b, WS2c$	$Investigation of moments using a meter ruler, pivot and balancing masses. (PAG P2)$
$P2.3m ☑ explain how levers and gears transmit the rotational effects of forces$	$an understanding of ratios and how this enables gears and levers to work as force multipliers$	$M1c$
$P2.3n ☑ recall that the pressure in fluids (gases and liquids) causes a net force at right angles to any surface$			$WS1.1b, WS1.2a, WS1.4a$	$Demonstration of balloons being pushed onto a single drawing pin versus many drawing pins.$
$P2.3o ☑ use the relationship between the force, the pressure and the area in contact$	$an understanding of how simple hydraulic systems work$	$M1a, M2a, M3a, M3b, M3c, M3d$

Learning outcomes

To include

Maths

Working scientifically

Practical suggestions

P2.3a explain that to stretch, bend or compress an object, more than one force has to be applied

applications to real life situations

WS1.1b, WS1.1e, WS1.2a, WS1.2b, WS1.2c, WS1.2e, WS1.3a, WS1.3c, WS1.3e, WS1.3f, WS1.3g, WS2a, WS2b, WS2c

Use of a liquorice bungee or spring to explore extension and stretching. (PAG P2)

P2.3b describe the difference between elastic and plastic deformation (distortions) caused by stretching forces

WS1.1b, WS1.1e, WS1.2a, WS1.2b, WS1.2c, WS1.2e, WS1.3a, WS1.3c, WS1.3e, WS1.3f, WS1.3g, WS2a, WS2b, WS2c

Comparisons of behaviour of springs and elastic bands when loading and unloading with weights. (PAG P2)

P2.3c describe the relationship between force and extension for a spring and other simple systems

graphical representation of the extension of a spring

M1a, M2a, M4a, M4b, M4c

WS1.1b, WS1.1e, WS1.2a, WS1.2b, WS1.2c, WS1.2e, WS1.3a, WS1.3c, WS1.3e, WS1.3f, WS1.3g, WS1.4f, WS2a, WS2b, WS2c

Investigation of forces on springs - Hooke’s law. (PAG P2)

P2.3d describe the difference between linear and non-linear relationships between force and extension

M1a, M2a, M4a, M4b, M4c

WS1.1b, WS1.1e, WS1.2a, WS1.2b, WS1.2c, WS1.2e, WS1.3a, WS1.3c, WS1.3e, WS1.3f, WS1.3g, WS2a, WS2b, WS2c

Investigation of the elastic limit of springs and other materials. (PAG P2)

P2.3e calculate a spring constant in linear cases

M1a, M2a, M3a, M3b, M3c, M3d

P2.3f calculate the work done in stretching

M1a, M2a, M3a, M3b, M3c, M3d, M4a, M4b, M4c, M4f

WS1.1b, WS1.2a, WS1.2b, WS1.2c, WS1.2e, WS1.3a, WS1.3c, WS1.3e, WS1.3f, WS1.3g, WS1.4f, WS2c

Use of data from stretching an elastic band with weights to plot a graph to calculate the work done. (PAG P2)

P2.3g describe that all matter has a gravitational field that causes attraction, and the field strength is much greater for massive objects

P2.3h define weight, describe how it is measured and describe the relationship between the weight of an object and the gravitational field strength, g

knowledge that the gravitational field strength is known as g and has a value of 10 N/kg at the Earth’s surface

WS1.1b

Calculations of weight on different planets.

P2.3i recall the acceleration in free fall

P2.3j ☑ apply formulae relating force, mass and relevant physical constants, including gravitational field strength, g, to explore how changes in these are inter-related

M1c, M3b, M3c

P2.3k ☑ describe examples in which forces cause rotation

location of pivot points and whether a resultant turning force will be in a clockwise or anticlockwise direction

P2.3l ☑ define and calculate the moment of a force

application of the principle of moments for objects which are balanced

M1a, M1c, M2a, M3a, M3b, M3c, M3d

WS1.2a, WS1.2b, WS1.3e, WS2a, WS2b, WS2c

Investigation of moments using a meter ruler, pivot and balancing masses. (PAG P2)

P2.3m ☑ explain how levers and gears transmit the rotational effects of forces

an understanding of ratios and how this enables gears and levers to work as force multipliers

M1c

P2.3n ☑ recall that the pressure in fluids (gases and liquids) causes a net force at right angles to any surface

WS1.1b, WS1.2a, WS1.4a

Demonstration of balloons being pushed onto a single drawing pin versus many drawing pins.

P2.3o ☑ use the relationship between the force, the pressure and the area in contact

an understanding of how simple hydraulic systems work

M1a, M2a, M3a, M3b, M3c, M3d

Forces in action

Next Steps

Learning Objectives