1. Mechanics – quiz 1 Physics12 Vectors, scalars & kinematics Mechanics – quiz 1 Physics12 Vectors, scalars & kinematics Quiz answers 1/ Define the term ‘mechanics’ 2a/ What are the scalar terms for ‘how far’ & ‘how fast’? 2b/ What are the vector terms for ‘how far’ & ‘how fast’? Mechanics is the study of how forces affect objects. SCALAR: distance & speed VECTOR: displacement & velocity

2. Mechanics – quiz 1 Physics12 Vectors, scalars & kinematics Mechanics – quiz 1 Physics12 Vectors, scalars & kinematics 3a/ How do you calculate average velocity? (equation) 3b/ What are the units of velocity? 4a/ Define instantaneous velocity? 4b/ How do you calculate instantaneous velocity? (ms -1 ) Instantaneous velocity is the velocity of an object measured at a point, and over a time that is small relative to the whole motion. Average velocity =total displacement total time Instantaneous velocity =ΔsΔs ΔtΔt =slope of s/t graph at a point

3. Mechanics – quiz 1 Physics12 Vectors, scalars & kinematics Mechanics – quiz 1 Physics12 Vectors, scalars & kinematics 5/ Define the term ‘acceleration’ and give its units. 6a/ A horse is running around a circular track at constant speed. Is it accelerating? YES 6b/ Explain your answer. (ms -2 ) Acceleration is the rate of change of velocity. Acceleration =change in velocity time taken for change Velocity is a vector term and includes direction. If the horse is changing direction then its velocity is changing, even though its speed does not change. Acceleration = change in velocity.

4. Mechanics – quiz 1 Physics12 Vectors, scalars & kinematics Mechanics – quiz 1 Physics12 Vectors, scalars & kinematics 7/ Define ‘kinematics’? 8/ What are s, u, v, a and t? Kinematics is the study of motion and moving objects. s = displacement u = initial velocity v = final velocity a = acceleration t = time

5. Mechanics – quiz 1 Physics12 Vectors, scalars & kinematics Mechanics – quiz 1 Physics12 Vectors, scalars & kinematics 9/ State what are the gradients of graphs of: (a) s/t (b) v/t (c) a/t 10/ Sketch s/t, v/t and a/t graphs for the following: (a) a man diving off a cliff into the sea (ignore AR) (b) a dog jumping up into the air to catch a ball (c) a girl on a trampoline (3 jumps) velocity acceleration rate of change of acceleration

6. Mechanics – quiz 1 Physics12 Vectors, scalars & kinematics 0 t 10(a) a man diving off a cliff into the sea (ignore AR) These graphs will be the same for any object falling from rest (not- moving) under the influence of gravity, ignoring air-resistance. The man’s displacement (from zero at sea-level) decreases as he falls. + s 0 v + - t 0 + a - His velocity (-) increases, due to gravity. His acceleration, due to gravity, is constant (-9.8 ms -2 )

7. Mechanics – quiz 1 Physics12 Vectors, scalars & kinematics 0 t 0 t 0 t - + - + - 9.8 ms -2 Slope = 0 Slope = + Slope = - Slope = constant & negative velocity = 0 10(b) a dog jumping up to catch a ball. These graphs will be the same for any object jumping, hopping or being thrown or fired upwards, (under the influence of gravity, ignoring air- resistance). The dog’s displacement (from zero at ground-level) increases then decreases. Its velocity (+) decreases, due to gravity, through zero (at the top of its jump) to (-) velocity when it lands. Its acceleration, due to gravity, is constant (-9.8 ms -2 ) s va +

8. Mechanics – quiz 1 Physics12 Vectors, scalars & kinematics 0 + 0 + - 0 + - t t t s v a 10(c) a girl on a trampoline These graphs will be the same for any object repeatedly jumping, hopping or bouncing (under gravity, ignoring air resistance).

9. Mechanics – quiz 1 Physics12 Vectors, scalars & kinematics