Topic 3 Kinematics

Question 1

Distance

Answer 1

distance travelled

scalar quantity

Question 2

Displacement

Answer 2

distance moved by an object in a particular direction

vector quantity

Question 3

Speed

Answer 3

the rate at which an object moves/ the rate at which distance is covered by an object.
v= d/t
scalar quantity

Question 4

instantaneous speed

Answer 4

speed at a particular moment

calculated by drawing a tangent on the graph

Question 5

velocity

Answer 5

speed in a particular direction
vector quantity 
v= s/t where s= change in displacement 
                      t= time taken 
                      v= velocity- ms^-1

Question 6

acceleration

Answer 6

the rate at which the object’s velocity is changing
vector quantity
a= change in velocity/ time taken

a= (v-u)/t

Question 7

how is displacement calculated using a velocity-time graph?

Answer 7

the area under the graph

Question 8

state what the gradients of the following graphs represent:
1- distance-time
2- displacement- time
3- velocity-time

Answer 8

speed
velocity
acceleration

Question 9

state the equations of motion that represent an object in uniform acceleration

Answer 9

v= u + at
s= (v+u)/2 * t 
s= ut + (at^2)/2
v^2 = u^2 + 2as

Question 10

the time for a projectile motion is determined by what?

Answer 10

vertical motion / vertical component of velocity

Question 11

what is the acceleration of free fall ?

Answer 11

9.81 m/s^2

Question 12

what is the range of a projectile?

Answer 12

it is the horizontal distance a projectile covers before it reaches the ground.

Question 13

how can the maximum range be achieved?

Answer 13

by throwing the projectile at an angle of 45 to the horizontal.

Question 14

Quadratic equation

Answer 14

ax^2 + bx + c = 0

x= (-b +/- square root b^2 - 4ac)/ 2a

Question 15

horizontal distance

Answer 15

horizontal velocity component * time taken

Question 16

horizontal velocity component

Answer 16

vcosO where v= initial velocity

O= angle to the vertical

Question 17

vertical velocity

Answer 17

vsinO where v= initial velocity

O= angle to the vertical

Question 18

what is the shape of the path of a projectile ?

Answer 18

Parabola

Question 19

state four different ways to measure speed

Answer 19

using:
2 light gates 
1 light gate 
ticker timer 
motion sensor

Question 20

which two methods are use to calculate the average speed.

Answer 20

2 or 1 light gate method

Question 21

which two methods are used to investigate motion of a moving object

Answer 21

ticker-timer and motion sensor

Question 22

how to calculate the initial and final velocity of the ‘interrupt’ card when measuring acceleration in a laboratory using a light gate?

Answer 22

u= l1/ t2-t1 where l1= length of the first section of the
interrupt card
t1= instant at which the card
section touched the light gate
t2= instant at which the card section
exited the light gate.

v= l2/ t4 - t3 where l2= length of the second section of
the interrupt card

Question 23

which method to calculate acceleration gives us an average value of a? and why?

Answer 23

light gate method - because v and u are average value. for the acceleration to be accurate, we would need instantaneous values of v and u.

Question 24

how to use the ticker-timer to calculate acceleration of an object ?

Answer 24

the practical arrangement is the same as for to measure its speed, i.e, the tape is connected to the trolley.
to interpret the tape we would need to divide the tape into sections, get average velocities of these sections and plot a graph of the velocity values to find the object’s acceleration.

Question 25

what is used to measure the acceleration of a free falling object?

Answer 25

it can be measured using an electronic timer, ticker-timer and a light gate.

Question 26

what are the equipment to measure acceleration using an electronic timer?

Answer 26

a stand, electromagnet, ball bearing, trapdoor, electronic timer.

Question 27

why may there be errors in the result while measuring acceleration of a free falling object?

Answer 27

using an electronic timer:
the electromagnet may gain some magnetism even when its turned off, this could slow down the ball’s fall and consequently disturb the results.

there may also be a mistake while measuring the height of the fall.

using a ticker-timer:
the friction between tape and ticker-timer may slow down the ball’s fall.