(b) (c) (d) (e) Answers Velocity & Displacement (p4 – 6) Scalar quantities have a magnitude only. Vector quantities have a magnitude and direction. Scalars: Speed, Distance, Mass, Time, Energy. Vectors: Force, Velocity, Displacement, Acceleration
(a) 10 m s-1 12 m s-1 30 s 48 s 360 m 7.5 m (a) 40 m 10m west 0.8 m s-1 0.2 m s-1 west (a) 0 m 8.89 m s-1 0 m s-1 (a) 700 m 500 m (053°) 0.78 m s-1 0.56 m s-1 (053°) (a) 18.3 m s-1 66 km h-1 13.0 m s-1 (140°) (a) 85.0 km h-1 46.1 km h-1 (283°) (a) 19.8 m s-1 15.4 m s-1 (260°) Acceleration (p7 – 8) (a) 2 m s-2 3 m s-2 9 m s-1 36 m s-1 4 s 4.2 s 2 m s-2 1.6 m s-2 22.5 s 9.9 m s-1 2.8 m s-1 -15 m s-2 0.1 m s-2 10 m s-2 Velocity-Time Graphs (p9 – 11) (a) Uniform acceleration Uniform deceleration Constant speed / zero acceleration Accelerates uniformly from rest. Stays at a constant speed. Decelerates uniformly until it has stopped. (a) 4 m s-2 8 m s-2 3 m s-2 -3 m s-2 (a) 56 m 12.6 m 43.5 m 118 m (a) A – ball is accelerating down towards ground. B – ball is bouncing on ground. C – ball is decelerating upwards. D – ball reaches highest E – ball is accelerating down towards ground. The ball is losing energy Weight (p12 – 13) Mass is a measure of how much of an object is there. It is measured in kg. Weight is a downward force caused by gravity. It is measured in N. (a) 30 N 2.25 N 30 kg 30 kg 8 N kg-1 26 N kg-1 (a) 30 N
1 N 650 N 12 000 N The weight of the space shuttle decreases. This is because: There is less mass due to fuel being used up. The shuttle is getting further away from the surface of the 85 kg (a) 372 N 2418 N 372 N 0 N 75 kg Saturn 13 N kg-1 Newton’s Laws (p14 – 19) (a) 2 N to the right 5.5 N to the right 4 N to the left 10 N to the left Speed, acceleration. (a) 120 N 135 N 1.5 kN 175 N (a) Teams remain at rest. 700 N 800 N Friction is a force that opposes motion. Tread on vehicle tyres, grips on shoes. Streamlined shape of vehicles, lubrication in engines. The object will accelerate in the direction of the unbalanced force. (a) 22.5 N 0.2 N 0.4 kg 40 kg 1.5 m s-2 1.5 m s-2 (a) 5 m s-2to the right 2 m s-2to the left 0.2 m s-2 to the 10 m s-2 to the left 1440 N Seat belts create an unbalanced force when a car brakes allowing a person to slow down with the car. Air bags and bumpers increase the time taken to slow down during a collision, reducing the force acting on a person. (a) Weight & air resistance Terminal velocity is the speed at which a falling object stops accelerating. 53 m s-1 A – Weight > Air resistance, so sky diver is accelerating. B – Weight = Air resistance, so sky diver has constant speed. C – Weight < Air resistance, so sky diver is decelerating. D – Weight = Air resistance, so sky diver has constant speed. (a) A hammer is more streamlined than a feather. There is no air resistance on the moon 1. 92 x 106 N 0.2 kg Equal, opposite, equal, opposite. (a) Hammer imparts a force on nail. Nail imparts a force back on to hammer. Foot imparts a force on ball. Ball imparts a force back on foot. Person pushes down on scales. Scales push back up on person. Shuttle pushes down. Gases push shuttle up. Work Done (p20 – 21) Work done is the energy transferred to an object. (a) 3000 J 155 J 2000 N 20 N 10 m 45 m 16 800 J 300 N 40 m