Question 1
Question: (i) Define the following terms:
(a)speed (b) velocity (c) uniform velocity (d) non uniform velocity
(e) acceleration (f) retardation.
(ii) Distinguish between:
(a) Speed and Velocity
(b) Uniform acceleration and Variable acceleration
Answer: (a) Speed
Speed is the distance travelled by a body in one second and is measured in metre per second (m s-1)
(b) Velocity
Velocity is the distance travelled by a body in a particular direction in unit time
Or
Velocity is defined as the rate of change of displacement. It is measured in metre per second (m s-1)
(c) Uniform Velocity
A body is said to travel with uniform velocity if it undergoes equal displacement in equal intervals of time, however small in a given direction
(d) Non-uniform Velocity
A body is said to be moving with non-uniform or variable velocity if
- it covers unequal distances in equal intervals of time or
- it covers equal distances in unequal intervals of time or
- it covers equal distances in equal intervals of time, but its direction is changing.
(e) Acceleration
Acceleration is defined as the rate of change of velocity
Or
Acceleration is the change in velocity in unit time. Its unit is m s-2
(f) Retardation
Retardation or deceleration is negative acceleration. If the velocity of a body is decreasing then the acceleration is negative and it is called retardation.
(ii)
(a) Speed and Velocity
(b) Uniform acceleration and Variable acceleration
Question 2
Question: Define Displacement.
Answer: Displacement is the distance travelled in a fixed direction.
Or
The shortest distance from the initial position to the final position of the body is called displacement.
Question 3
Question: Calculate the distance covered and displacement of an object following the path as shown in the figure below.
a)
(b)
(c)
Answer: a) ACB is a semicircular path of radius r.
Distance covered = circumference of the hemisphere = pr
displacement = diameter = 2r. (i.e., the shortest distance between A and B)
b) Here the body is thrown vertically up to a height 'h' and the body returns back to the ground level.
Distance = h + h = 2h
Displacement = h - h = 0
(-ve to show the change in direction)
(c) In this case the body is thrown vertically up from a height h above the ground.
It travels an additional distance h' and comes back to the ground
distance = h1 + h1 + h
= h + 2h1
displacement = h1 - h1 - h = - h
(-ve sign to show change in direction)
Question 4
Question: Convert 1 km/h to m/s.
Answer: 
i.e.,
Question 5
Question: What is the relationship between the distance (S) and time(t) for a body moving with uniform velocity(v)?
Answer: S = vt
Question 6
Question: Draw a diagram to show the motion of a body whose speed remains constant but velocity changes continuously.
Answer: 
If a body moves along a circle with uniform speed, though the speed is constant its velocity changes continuously as the velocity of the body at any point is along the tangent to the circle at that point as shown in figure.
Question 7
Question: A scooter travels a distance of 600 m in 20 seconds southwards.
(a) What is the speed of the scooter?
(b) What is the velocity of the scooter?
Answer: (a) Speed = 
= 30 m/s
(b) Velocity of the scooter = 30 m/s due south.
Question 8
Question: Give an example of a body moving with a uniform speed but variable velocity.
Answer: A body moving along the circumference of a circle.
e.g., Revolution of the earth around the sun.
Question 9
Question: A train moving with a uniform speed covers a distance of 1200 m in 20 s. Calculate (i) the velocity of the train (ii) the time taken to cover 3000 m.
Answer: (i) Velocity 
= 60 m s-1
(ii) Time 
= 50 s
Question 10
Question: A body travels from A to B in 10 seconds with a speed of 50 km/h and returns with a speed of 100 km/h in 5 s. Find the average speed. Also find the average velocity for the whole journey.
Answer: Distance from A to B = Speed x time
= 50 km/h x 10 s
Total distance from A to B both ways 
Total time taken = 10 + 5
= 15 s
Average speed 
= 18.5 m s-1
Average velocity 
= 0 km/h
Displacement is zero, because the body has come back to its initial position.
Note :
To convert km/h to m/s, multiply by 5/18 and to convert m/s to km/k, multiply by 18/5
