1If a steel spring is stretched as far as possible, will it return to its original state?
2Write the differences between a displacement time graph and a speed time graph.
3Write the differences between inertia of rest and inertia of motion.
4Write the differences between elasticity and plasticity.
5A motorcycle, a car, a truck, a bus and a train moving with the same speed take different times to come to rest. Give the reason.
6When a tree is shaken, leaves and fruits fall down. Give the reason.
7During a bus journey a passenger kept a bag on the floor beside the seat, and some time after the bus started moving found the bag near the seat in front. Give the reason.
8A gun must be held against a firm support while firing. Give the reason.
9Two rubber balls of the same size were dropped together on the floor, and one bounced higher. Give the reason.
10A rubber band should not be stretched beyond a certain limit. Give the reason.
11Define average speed and acceleration.
12Prove the equations of motion in a straight line: \( v = u + at \), \( v^2 = u^2 + 2as \) and \( s = ut + \frac{1}{2}at^2 \).
13Draw one displacement time graph and one speed time graph to show a body moving with uniform speed in a straight line.
14For time (s) 0, 2, 4, 6, 8, 10, 12, 14 the displacement (m) is 0, 4, 8, 8, 12, 8, 4, 0. Draw the displacement time graph, describe the nature of the motion from its slope, and calculate the average velocity for the first 4 s.
15On a displacement time graph of the hare and tortoise race, the hare's line is steep at first, then parallel to the x-axis for a long while, then steep again at the end, while the tortoise's line is one straight line of constant slope from start to finish. Observing the graph, write the story of the race from beginning to end.
16What is inertia? Write two examples each of inertia of rest and inertia of motion.
17Write the relation between mass and inertia.
18State Newton's first law of motion.
19Write two examples to show that a resultant force changes the state of a body.
20On the basis of high speed and Newton's first law of motion, explain the bus accidents that can happen at mountain bends.
21State Newton's second law of motion and prove that \( F = ma \).
22State Newton's third law of motion.
23Write two examples each of daily life activities based on all three of Newton's laws of motion.
24Find any two applications each of Newton's first, second and third laws of motion and write them in a table showing the activity, the law used and the explanation.
25Separate the action and the reaction when a badminton racket hits a shuttlecock and when a person steps off a boat onto the bank.
26Define elasticity and plasticity with examples.
27An aeroplane starting from rest on a runway toward the south gains a uniform acceleration of 1.5 m/s² and lifts off the ground after 30 s. Calculate the displacement it covers on the runway and its velocity just before take off.
28Rohan dropped a stone from the top of a bridge into the river, and Suraj, sitting by the river below, used a stopwatch to find that the stone took 2 s to reach the water surface. Taking the acceleration of the falling stone as 9.8 m/s², calculate the height of the bridge above the water surface.
29Suraj's mass is 50 kg and the mass of his bicycle is 12 kg. While riding downhill an acceleration of 2 m/s² was produced. Calculate the resultant force acting on the bicycle in that condition.
30A car of mass 1500 kg was moving at 72 km/h. When the driver applied the brakes, its speed became 10 km/h after covering 50 m. Calculate the resultant force acting on the car during this period.
31The motion of a bus travelling east is shown on a speed time graph: a straight line from A (0 s, 0 m/s) to B (4 s, 10 m/s), a line parallel to the time axis from B to C (6 s, 10 m/s), a straight line from C to D (10 s, 25 m/s), a parallel line from D to E (12 s, 25 m/s), a straight line from E to F (16 s, 30 m/s), and a curved line from F to G (20 s, 20 m/s). (a) Separate the segments of uniform speed, uniform acceleration, non uniform acceleration and retardation. (b) Among the uniform acceleration segments, in which one did the speed change fastest? (c) What is the acceleration of the bus between C and D? (d) Calculate the displacement of the bus from C to D.
32Why is steel used to build strong houses and bridges?
33What is a restoring force? In which kind of body does it develop?