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Physics Part-I
Class 11
NCERT
1
Chapter 1: Physical World
16 questions
2
Chapter 2: Units and Measurements
51 questions
3
Chapter 3: Motion in Straight Line
50 questions
4
Chapter 4: Motion in a Plane
43 questions
5
Chapter 5: Laws of motion
52 questions
Q1
The speed of the stone is increased beyond the maximum permissible value, and the string breaks suddenly, which of the following correctly describes the trajectory of the stone after the string breaks:
(a) the stone moves radially outwards,
(b) the stone flies off tangentially from the instant the string breaks,
(c) the stone flies off at an angle with the tangent whose magnitude depends on the speed of the particle.
Q2
Explain why
(a) A horse cannot pull a cart and run in empty space.
(b) Passengers are thrown forward from their seats when a speeding bus stops suddenly.
(c) It is easier to pull a lawn mower than to push it.
(d) A cricketer moves his hands backwards while holding a catch.
Q3
Figure above shows the position-time graph of a body of mass . Suggest a suitable physical context for this motion. What is the time between two consecutive impulses received by the body? What is the magnitude of each impulse?
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Chapter 6: Work, Energy and Power
41 questions
7
Chapter 7: System of Particles and Rotational Motion
45 questions
8
Chapter 8: Gravitation
33 questions
Question
Easy
Solving time: 2 mins
Explain why(a) A horse cannot pull a cart and run in empty space.(b) Passengers are thrown forward from their seats when a speeding bus stops suddenly.(c) It is easier to pull a lawn mower than to push it.(d) A cricketer moves his hands backwards while holding a catch.
Explain why
(a) A horse cannot pull a cart and run in empty space.
(b) Passengers are thrown forward from their seats when a speeding bus stops suddenly.
(c) It is easier to pull a lawn mower than to push it.
(d) A cricketer moves his hands backwards while holding a catch.
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Text solution
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(a) While trying to pull a cart, a horse pushes the ground backward with some force. The ground, in turn, exerts an equal and opposite reaction force upon the feet of the horse. This reaction force causes the horse to move forward.
An empty space is devoid of any such reaction force. Therefore, a horse cannot pull a cart and run in empty space.
(b) This is due to inertia of motion. When a speeding bus stops suddenly, the lower part of a passenger's body, which is in contact with the seat, suddenly comes to rest. However, the upper part tends to remain in motion (as per the first law of motion). As a result, the passenger's upper body is thrown forward in the direction in which the bus was moving.
(c) While pulling a lawn mower, a force at an angle is applied on it, as shown in the given figure.
The vertical component of this applied force acts upward. This reduces the effective weight of the mower.
On the other hand, while pushing a lawn mower, a force at an angle is applied to it, as shown in the following figure.
In this case, the vertical component of the applied force acts in the direction of the weight of the mower. This increases the effective weight of the mower.
Since the effective weight of the lawn mower is lesser in the first case, pulling the lawn mower is easier than pushing it.
(d) According to Newtons second law of motion, we have the equation of motion:
F = ma = m v /t ...(i)
Where,
F = Stopping force experienced by the cricketer as he catches the ball
m = Mass of the ball
t = Time of impact of the ball with the hand
It can be inferred from equation (i) that the impact force is inversely proportional to the impact time, i.e.,
F1/t ...(ii)Equation (ii) shows that the force experienced by the cricketer decreases if the time of impact increases and vice versa.
While taking a catch, a cricketer moves his hand backward so as to increase the time of impact (t). This is turn results in the decrease in the stopping force, thereby preventing the hands of the cricketer from getting hurt.
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Practice more questions from Physics Part-I (NCERT)
Q1
The speed of the stone is increased beyond the maximum permissible value, and the string breaks suddenly, which of the following correctly describes the trajectory of the stone after the string breaks:
(a) the stone moves radially outwards,
(b) the stone flies off tangentially from the instant the string breaks,
(c) the stone flies off at an angle with the tangent whose magnitude depends on the speed of the particle.
Q2
Explain why
(a) A horse cannot pull a cart and run in empty space.
(b) Passengers are thrown forward from their seats when a speeding bus stops suddenly.
(c) It is easier to pull a lawn mower than to push it.
(d) A cricketer moves his hands backwards while holding a catch.
Q3
Figure above shows the position-time graph of a body of mass . Suggest a suitable physical context for this motion. What is the time between two consecutive impulses received by the body? What is the magnitude of each impulse?
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| Question Text | Explain why (a) A horse cannot pull a cart and run in empty space. (b) Passengers are thrown forward from their seats when a speeding bus stops suddenly. (c) It is easier to pull a lawn mower than to push it. (d) A cricketer moves his hands backwards while holding a catch. |
| Updated On | Jun 7, 2022 |
| Topic | Laws of motion |
| Subject | Physics |
| Class | Class 11 |
| Answer Type | Text solution:1 Video solution: 1 |
| Upvotes | 124 |
| Avg. Video Duration | 2 min |
