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SS1: PHYSICS – 1ST TERM

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  1. Introduction to Physics | Week 1
    4Topics
    |
    1 Quiz
  2. Measurement | Week 2
    3Topics
  3. Measurement of Mass | Week 3
    6Topics
    |
    1 Quiz
  4. Motion | Week 4
    5Topics
    |
    1 Quiz
  5. Velocity-Time Graph | Week 5
    4Topics
    |
    1 Quiz
  6. Causes of Motion | Week 6
    5Topics
    |
    1 Quiz
  7. Work, Energy & Power | Week 7
    3Topics
  8. Energy Transformation / Power | Week 8
    3Topics
    |
    1 Quiz
  9. Heat Energy | Week 9
    5Topics
    |
    1 Quiz
  10. Linear Expansion | Week 10
    6Topics
    |
    1 Quiz
Lesson Progress
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Combining the V-t graphs

The total distance travelled is the total area under the graph from the graph, the shape is that of a trapezium.

 ∴ Total distance covered = Area of a trapezium

=   \( \frac{1}{2}\)(Sum of parallel sides) x h

=   \( \frac{1}{2} \scriptsize (a \: + \: b) \: \times \: h\)

Also, breaking the graph into components, S1, S2, S3

S1 is a right angle triangle = distance covered = Area of a right angle triangle

S1 = \( \frac{1}{2} \scriptsize \: \times \: base \: \times \: height \\ = \frac{1}{2} \scriptsize bh\)  

S2 = Area of a rectangle = total distance covered = L x b

S3 = Area of a right angle triangle = \( \frac{1}{2} \scriptsize \: \times \: base \: \: \times \: height \\ =\frac{1}{2} \scriptsize bh \)

 ∴ the total distance covered = S1 S2 + S3

= \(\normalsize \frac{1}{2} \scriptsize bh \: + \: (L \: \times \: b) \: + \: \normalsize \frac{1}{2} \scriptsize bh \)

Examples:

i. A car is travelling with initial velocity of 30ms-1 and attains a final velocity of 80ms-1 in 20seconds. Find the acceleration of the car.

Solution: u = 30ms-1, v = 80ms-1, t = 20seconds

a = \( \frac {v \: – \: u}{t} \\ = \frac {80\: – \: 30}{20} \\ = \frac {50}{20} \\= \scriptsize 2.5ms^{-2}\)

ii. A Toyota car started from rest and accelerated to 4.0 m/s for 2 seconds. The car then moved with uniform velocity for 4 seconds. When the brakes were applied, the car slowed down to a stop for 2 seconds.

Calculate: (a) the acceleration of the car. (b) the deceleration of the car. (c) the distance travelled by car in each phase of the motion.  (d) the total distance travelled.

comined v t graph e1606893609845

a. When the car accelerated from rest to 4.0 m/s, u = 0 m/s, v = 4.0 m/s, time, t = 2 seconds.

acceleration = \( \frac {v \: – \: u}{t} \\ = \frac {4 \: – \: 0}{2} \)

acceleration = 2ms-2

b. When the brakes were applied, the car decelerated ( i.e slowed down) from 4.0 m/s to 0 m/s for 2 seconds.  

Then, u = 1.0 m/s, v = 0 m/s, t = 2 seconds.  

deceleration = \( \frac {v \: – \: u}{t} \\ = \frac {0 \: – \: 4}{2} \)

acceleration = – 2ms-2

c. In phase 1 (acceleration stage)

phase 1 e1606894254553

Distance covered = Area of a right angle triangle

Distance covered = \( \frac{1}{2} \scriptsize\: \times \: b \: \times \: h \\ = \frac{1}{2}\scriptsize\: \times \: 2s \: \times \: 4ms^{-1} \\ \scriptsize = 4 m \)

In phase 2 (uniform velocity stage)

phase 2 e1606894692276

Area of a square = total distance covered = l x b = 4m/s x 4s = 16m

In phase 3 (deceleration stage)

decelerarion stage e1606894958729

Distance covered = Area of a right angle triangle

Distance covered = \( \frac{1}{2} \scriptsize \: \times \: b \: \times \: h \\ = \frac{1}{2} \scriptsize\: \times \: 2s \: \times \: 4ms^{-1} \\ \scriptsize = 4 m \)

d. The total distance travelled = phase 1 + phase 3 + phase 3

= 4m + 16m + 4m = 24m

OR

Total distance covered = Area of a trapezium

:- \( \frac{1}{2} \scriptsize\: \times \: (a \: + \: b) \: \times \: h \\ = \frac{1}{2} \scriptsize \: \times \: (4 \: + \: 8) \: \times \: 4 \\ \scriptsize = 6 \: \times \: 4 \\ \scriptsize = 24m \)

Evaluation Questions

1. Define (i) Velocity.

(ii) Acceleration

2. A body accelerates from rest and moves with a uniform acceleration of 10m/s2. What distance does it cover in the last one second of its motion?

3. A car is brought to rest from a speed of 25m/s in 10 seconds. Find the retardation.

4. A mango dropped from a height of 100m above the ground. Calculate the velocity of the mango just before hitting the ground.

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