Questions 15 and 16 40km/hr – 0km/hr / 5s = 8km/hr/s 50km/hr – 0km/hr / 5s = 10km/hr/s Car B accelerates fastest 1 st row- no motion, constant velocity 2 nd row- constant velocity, positive acceleration 3 rd row- positive acceleration, negative acceleration
Questions 17 & 18 “g” = 9.8m/s2 and is acceleration due to gravity 9.8 x 2 = 19.6 m/s
Questions 19 & 20 Newton’s 1 st law defines inertia as it describes an object’s resistance to change in motion Inertia is resistance to change in motion Example: a car crash
Questions 21 & 22 A force is a push or a pull and is measured in Newtons Balanced force- net force of 0, objects’ motion does not change Unbalanced force- net force that accelerates an object Net force- the sum of all forces acting on an object
Question 23 The acceleration of an object is dependent on the force applied and the mass of the object. To accelerate an object the force must be applied in the same direction as the acceleration.
Questions 24 & 25 F = 1500kg x 2.5 m/s2 = 3750N M = 500N / 2.0 m/s2 = 250 kg
Question 26 Mass is the amount of matter in an object. It is constant and is measured in kg Weight is the measure of the pull of gravity on an object. It is a force and is measured in Newtons.
Questions 27 & 28 W = mass x 9.8m/s2 ( W = mg) M = weight / 9.8m/s2 (M = w/g) Inertia is NOT dependent on gravity because inertia is determined by mass and mass is a constant.
Questions 29 & 30 Gravity is the force of attraction between all objects in the universe. Gravitational attraction depends on the mass of the 2 objects and the distance between them There is not enough mass
Question 31 For every action there is an equal and opposite reaction.
Question 32 The swimmer pushes on the water and the water pushes back The ball pushes on the wall and the wall pushes back. The diver pushes down on the raft and the raft pushes back. The person pushes on the wall and the wall pushes back.
Questions 33-35 Air resistance pushes up as gravity pulls down. Friction is the force that opposes motion between 2 objects that are touching. An object in free fall has no other force acting on it but gravity.