PHYSICS
1. (a) Identify the kind of motion in the following cases:
(0) A car moving with constant speed turning around a curve. No
(in) An electron orbitting around nucleus.
(b) An artificial satellite is moving in a circular orbit of radius 36,000 km. Calculate its speed if it
takes 24 hours to revolve around the earth.
2. (a) Define average speed
(b) A bus travels a distance of 120 km with a speed of 40 km/h and returns with a speed of 30
km/h. Calculate the average speed for the entire journey.
3. Define uniform and non-uniform motion. Write one example for each
4. What does the odometer of an automobile measure? Which of the following is moving faster?
Justify your answer.
( A scooter moving with a speed of 300 m per 1 minute.
(ii) A car moving with a speed of 36 km per hour
5. A car travels from stop A to stop B with a speed of 30 km/h and then returns back to A with a
speed of 50 km/h. Find
(i) displacement of the car
(ii) distance travelled by the car.
(iii) average speed of the car.
6. Velocity-time graph for the motion of an object in a straight path is a straight line parallel to the
time axis
(a) Identify the nature of motion of the body,
(b) Find the acceleration of the body.
(c) Draw the shape of distance-time graph for this type of motion.
Answers
Explanation:
uniform motion
a body is said to have a uniform motion,if it travels equal distance in equal intervals of time.
non-uniform
if it travel unequal distance in equal intervals of time .
average speed
ratio of the total distance travelled by a body to the total time taken.
average speed =total distance travelled/total time taken
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Ans 1) a) i - Circular Motion
ii - Circular motion
b) Radius = 36000 km
Circumference = 2πr
= 2×22/7× 36000
= 22685.71
Now here circumference = Distance of the path travelled (orbit)
Also we know that the moon travels its orbit once in 24hrs
Thus Distance = 22685.71429
Let Speed = x
Time taken = 24 hrs
Also, Speed = Distance/Time
Thus, x = 22685.71/24
Speed = 9428.57 km/hr
Ans 2) a) The total distance by total time is called average speed
b) Total Distance = 120 + 120 = 240m
Time 1 = 120/40 = 3 h
Time 2 = 120/ 30 = 4h
Hence, Total Time = 7 h
Therefore,
Avg speed = 240/7 = 34.14 km/h
Ans 3) Uniform Motion
If an object covers equal distances in equal intervals of time then it is said to be uniform motion. Example:-Movement of hands of Clock
Non- Uniform Motion
If an object covers unequal distances in equal interval of time then it is said to be non- uniform motion. Example:- A person who is jogging and then walking.
Ans 4) Odometer measures distance an automobile.
i) a) V=S/t
= 300/60
= 5m/s
b) V= S/t
= 36/1000x60x60/1
= 129.6m/s
b) car is moving faster than a).
Ans 5) Displacement is the shortest distance between the initial and the final position. Here, the car travels from stop A to B and returns to stop A.
Thus, the displacement of the car is 0 m/s.
let the distance travelled by the car from stop A to B = x km
The car travels from A to B and returns back to B. Thus,
total distance travelled = 2x km
Time while going from A to B = Distance travelled / Speed taken
= x/30 hours
Time while returning from stop B to A = x/50 hours
Ans 6)This means velocity is not changing with time and there is uniform motion in the body with a constant velocity in a fixed direction but acceleration is Zero, as there is no slope in the graph as well.
a) The nature of motion of the body is Uniform.
b) The acceleration is zero.
c) The graph is attached to the answer.
Ans 7) Initial speed of the bus, u= 0 m/s
Acceleration, a = 0.1 m/s2
Time taken, t = 2 minutes = 120 s
(a) v= u + at
v= 0 + 0×1 × 120
v= 12 ms-1
(b) According to the third equation of motion, v2 - u2= 2as
S is the distance covered by the bus
(12)2 - (0)2= 2(0.1) s
S = 720 m
Speed acquired finally by the bus is 12 m/s.
Distance travelled by the bus is 720 m.