What is a force? What 3 things can forces do? Label the forces acting on this car. Can you identify the interaction pairs? Forces Y7 Forces can be balanced or unbalanced. The size of the arrow tells you which force is bigger or smaller. For each of the diagrams, draw and label 2 force arrows. Name each of these contact forces: f_______ is greatest on r________ surfaces. u________ a__ _______ Car accelerating The larger the surface area the _________ the force. A parachute falling Name each of these non-contact forces: Car at constant speed Object floating on water Object staying floating in the middle of water _________ _________ _________ The closer the object the ___________ the force

Gravity, Weight and Mass Hooke’s Law and Extension What is Hooke’s Law?: __________________ ______________________________________ Data interpretation: M___________ measures how much material an object is made of. It is measured in k__________________. W________ measures the force of gravity on an object. Because w_________ is a force, it is measured in N_______________. _______ never changes. _______ changes because it is a force affected by the size of gravity; the bigger the mass, the ________ the weight. Extension of spring (cm) Gravitational field strength, mass and weight Weight (N) = mass (kg) x gravitational field strength (N/kg) Complete the table: Which planet has the smallest g? Looking at the g for Jupiter, what can you deduce about the mass (size) of Jupiter compared to the mass of Earth? Weight (N) Planet Your mass (kg) Gravitational field strength (N/kg) Your weight on the planet (N) Mercury   3.7 Earth  50kg 10.0 Jupiter  1155 Neptune 11.0 Pluto 0.7 What is the extension of the spring at 2.6N? What force is required to extend the spring by 12cm? Up to 6N, does the spring follow Hooke’s law? Explain. After 7N, what happens? Why?