What types of motions are represented by the following velocity-time graphs?
(a) Since the velocity-time graph is a straight line, the body has uniform velocity.
(b) The body has uniform acceleration and its initial velocity is zero because the lne starts from the origin.
(c) The body has some initial velocity and is under uniform retardation.
(d) The body has some initial velocity and uniform acceleration.
(e) The body has zero initial velocity and it has variable acceleration.
(f) The body is at rest from O to A, it has uniform acceleration from A to B, it has uniform velocity from B to C and from C to D, the body is under uniform retardation.
A driver of a car travelling at 52 km h–1 applies the brakes and accelerates uniformly in the opposite direction. The car stops in 5 s. Another driver going at 34 km h–1 in another car applies his brakes slowly and stops in 10 s. On the same graph paper, plot the speed versus time graphs for the two cars. Which of the two cars travelled farther after the brakes were applied?
In Fig. 8.50, AB and CD are the speed-time graphs for the two cars whose initial speeds are 52 km/h and 34 km/h, respectively. In Fig. AB and CD are the speed-time graphs for the two cars whose initial speeds are 52 km/h and 34 km/h, respectively.
Fig. shows the distance-time graph of three objects A, B and C. Study the graph and answer the following questions:
(a) Which of the three is travelling the fastest?
(b) Are all three ever at the same point on the road?
(c) How far has C travelled when B passes A?
(d) How far has B travelled by the time it passes C?
Thus, B is travelling the fastest. Ans.
(ii) No, all three do not meet at any point on the road. Ans.
(iii) When B passes A at point N (at 1.2 hours), C is at a distance of 8 km from the origin O. Ans.
(iv) B passes C at 0.7 hours. During this time B covers distance = 6 km. Ans.
Abdul, while driving to school, computes the average speed for his trip to be 20 km h-1. On his return trip along the same route, there is less traffic and the average speed is 30 km h-1. What is the average speed for Abdul’s trip?
Describe the various types of motions observed in bodies.
Various types of motion as observed in bodies are:
1. Translatory motion: When a body moves as a whole along a straight or curved path, it is said to be in translatory motion.
Translatory motion is again of two types:
(i) Rectilinear motion: Here a body moves as a whole along a straight path.
For example, a train moving on straight rails has translatory rectilinear motion.
(ii) Curvilinear motion: In this case a body moves as a whole along a curved path.
For example, motion of a bicycle taking a turn along a curved path.
2. Rotatory motion: When a body rotates about a fixed point or axis, it exhibits a rotatory motion.
For example, motion of a flywheel about a shaft.
3. Vibratory or oscillatory motion: When a body moves to and fro about a mean position, the motion is said to be vibratory or oscillatory motion.
For example, the motion of the pendulum of a wall-clock.
4. Complex motion: When the motion of a body may be a combination of more than one types of motion, it is said to be a complex motion.
For example, a ball rolling down an inclined plane has both translatory and rotatory motions.