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2 of 43  A force (F) is a push, pull or twist. It cannot be seen but you can see how a force affects an object.

3 of 43  The strength of a force is measured in newtons (N).  1 Newton is the amount of force needed to make a 1kg object accelerate to 1m/s 2 in the absence of an opposing force.  Measured using a force meter.

4 of 43 Thrust Friction Weight Support / Lift Object

5 of 43  The resulting force (net force) on an object can be found by combining forces.  If two forces are acting in the same direction they are added.  If two forces are acting in opposite directions they are subtracted.

6 of 43  If two equal size forces act in opposite directions on an object the net force is... F = 15 N Net Force = 15N - 15N = 0N  Balanced forces do not change the motion of an object. Zero.

7 of 43  If a pair of opposing forces are unequal the net force is not Zero. F = 15 NF = 25 N Net Force = 25N - 15N = 10N right  Unbalanced forces will cause an object to accelerate, decelerate or change directions.

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9 of 43 The ship is floating on the water. Which forces are acting on the ship? Weight Support Because Gravity and Support are equal the ship stays afloat.

10 of 43 Gravity is acting on the elephant and there is much less air resistance. Weight Because the forces are unbalanced the elephant accelerates downward. Support

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12 of 43  If the forces on an object are balanced: If the object is stationary, it will remain stationary. If the object is moving, it will continue to move at the same speed and in a straight line.  The object will continue to do what it is already doing without any change.

13 of 43  If the forces are unbalanced, two things can happen: The speed can change. The object will accelerate or decelerate. The direction of motion can change.

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15 of 43 Force = Mass × Acceleration  Mass must be in kg  Acceleration in m/s 2  Force in N F m a

16 of 43  Mass is the amount of matter in an object. Measured in kg.  Mass can be measured using a balance or a scale.  Weight is the force of gravity (F g ) pulling downwards on an object. Measured in N.

17 of 43 Weight = Mass ×  Mass must be in kg  Acceleration in m/s 2  Weight Force in N  Acceleration due to gravity is 10 m/s 2 FgFg m g Acceleration due to Gravity

18 of 43  If your mass was 60 kg then your weight force would be 600 N.  Mass = 79 kgWeight =  Mass = 115 kgWeight =  Mass = Weight = 432 N 43.2 kg 790 N 1150 N

19 of 43  Where is weight the greatest?  Where is mass the greatest?

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21 of 43  Ariana wins a competition for a Tandem Skydive. The plane flies to a height of m above sea level. Ariana is strapped to her jumpmaster. Ariana and the jumpmaster have a combined mass of 150 kg. a) Using the equation F g = mg find the combined weight of Ariana and the jumpmaster. Weight = __________ N A

22 of 43  During the first 10 seconds the net force acting on Ariana and the jumpmaster is 825 N. c) Calculate the net acceleration of Ariana and the jumpmaster. Include an appropriate unit. Net acceleration = __________ M 5.5 m/s 2

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25 of 43 The speed of an object can be calculated using this equation: distance travelled time taken speed = Speed is measured in metres per second (m/s). Distance travelled is measured in metres (m). Time taken is measured in seconds (s). The standard unit for speed in physics is m/s, but other units such as kilometres per hour (km/h) are more convenient when measuring the speed of vehicles. Why is this?

26 of 43 Speed is a measure of how far an object moves in a given time. This jet is travelling at 350 m/s. This means the jet travels 350 metres every second. This car is travelling at 60 mph. This means the car travels 60 miles every hour.

27 of 43 The speed of an object does not depend on the direction in which it is travelling. The velocity of an object is the speed and direction in which it is moving. The car is travelling north with a velocity of 10 m/s. Is velocity different to speed? As the car goes round the corner, the speed of the car remains constant but the velocity changes.

28 of 43 What is the speed of the object between points A and B? time (s) distance (m) A B the object has moved 60 m ( ) it took 3 s to move this distance (6 - 3) speed = distance/time = 60/3 = 20 m/s

29 of 43 Calculating speed from graphs

30 of 43 The acceleration of an object can be calculated using this equation: change in speed time taken acceleration = Acceleration is measured in metres per second per second (m/s 2 ). Change in speed is measured in metres per second (m/s). Time taken is measured in seconds (s).

31 of 43 This gradient of the line in a speed– time graph represents acceleration How can the acceleration of an object be calculated from a speed–time graph? If the gradient goes up, the object has a positive acceleration. If the gradient goes down, the object has a negative acceleration, or deceleration. time spee d time spee d

32 of 43 What is the acceleration of the object between points A and B? time (s) speed (m/s) A B the object’s speed has increased by 20 m/s (25 - 5) it took 4 s to change speed (6 - 2) acceleration = speed/time = 20/4 = 5 m/s 2

33 of 43 Calculating acceleration from graphs

34 of 43 The work done on an object can be calculated using this equation: work done = force x distance moved Distance moved is measured in metres (m). Work done is measured in joules (j). Force is measured in newtons (N).

35 of 43 Factors affecting work done

36 of 43 A cyclist peddles a bicycle with a force of 1,000 N moving it 250 m. Calculating work done question 1 = 1,000 x 250 = 250,000 J = 250 kJ = force x distance work done How much work has been done by the cyclist?