Home
Class 12
PHYSICS
Explain why (a) A horse cannot pull a ...

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 ) A cricketer moves his hands backwards when holding a catch.

Text Solution

Verified by Experts

(a) The horse-cart system has no external force in empty space. The mutual forces between the horse and the cart cancel each other (Third Law). On the ground the contack force between the system and the ground (friction) causes their motion from rest.
(b) Due to inertia of parts of the body which are not directly in contact with the seat.
(c) A lawn mover is pulled or pushed by applying force at an angle. When we push, the normal force (N) must be more than its weight, for equilibrium in the vertical direction. This results in greater fricition `f(fpropN)` and, therefore, a greater applied force to move. Just the opposite happends while pulling.
(d) To reduce the rate of change of momentum and hence to reduce the force necessary to stop the ball.
Promotional Banner

Topper's Solved these Questions

  • NEWTONS LAWS OF MOTION

    ALLEN|Exercise EXERCISE-I|52 Videos

  • NEWTONS LAWS OF MOTION

    ALLEN|Exercise EXERCISE-II|112 Videos

  • NEWTONS LAWS OF MOTION

    ALLEN|Exercise EXERCISE-III|28 Videos

  • NEWTON'S LAWS OF MOTION & FRICTION

    ALLEN|Exercise EXERCISE (JA)|4 Videos

  • RACE

    ALLEN|Exercise Basic Maths (Wave Motion & Dopplers Effect) (Stationary waves & doppler effect, beats)|24 Videos

Similar Questions

Explore conceptually related problems

Explain why a horse cannot pull a cart and run in empty space

When a speeding bus stop suddenly, passengers are thrown forward from their seats because

Why do you fall in the forward direction when a moving bus brakes to a stop and fall backwards when it accelerates from rest?

Explain the following When a train suddenly moves forward, the passenger standing in the compartment tends to fall backwards.

An inquistive student, determined to test the law of gravity for himself, walks to the top of a building og 145 floors, with every floor of height 4 m, having a stopwatch in his hand (the first floor is at a height of 4 m from the ground level). From there he jumps off with negligible speed and hence starts rolling freely. A rocketeer arrives at the scene 5 s later and dives off from the top of the building to save the student. The rocketeer leaves the roof with an initial downward speed v_0 . In order to catch the student at a sufficiently great height above ground so that the rocketeer and the student slow down and arrive at the ground with zero velocity. The upward acceleration that accomplishes this is provided by rocketeer's jet pack, which he turns on just as he catches the student, before the rocketeer is in free fall. To prevent any discomfort to the student, the magnitude of the acceleration of the rocketeer and the student as they move downward together should not exceed 5 g. Just as the student starts his free fall, he presses the button of the stopwatch. When he reaches at the top of 100th floor, he has observed the reading of stopwatch as 00:00:06:00. What should be the initial downward speed of the rocketeer so that he catches the student at the top of 100 the floor for safe landing ?

An inquistive student, determined to test the law of gravity for himself, walks to the top of a building og 145 floors, with every floor of height 4 m, having a stopwatch in his hand (the first floor is at a height of 4 m from the ground level). From there he jumps off with negligible speed and hence starts rolling freely. A rocketeer arrives at the scene 5 s later and dives off from the top of the building to save the student. The rocketeer leaves the roof with an initial downward speed v_0 . In order to catch the student at a sufficiently great height above ground so that the rocketeer and the student slow down and arrive at the ground with zero velocity. The upward acceleration that accomplishes this is provided by rocketeer's jet pack, which he turns on just as he catches the student, before the rocketeer is in free fall. To prevent any discomfort to the student, the magnitude of the acceleration of the rocketeer and the student as they move downward together should not exceed 5 g. Just as the student starts his free fall, he presses the button of the stopwatch. When he reaches at the top of 100th floor, he has observed the reading of stopwatch as 00:00:06:00 (hh:mm:ss:100 th part of the second). Find the value of g. (correct upt ot two decimal places).

“When a train suddenly moves forward, the passenger standing in the compartment tends to fall backwards". Explain.

State whether the following statements are true or false by writing T/F against them. (a) Earth moves around Sun with a uniform velocity. (b) The motion of moon around Earth in a circular path is an accelerated motion. ( c) A uniform linear motion is unaccelerated, while a uniform circular motion is an accelerated motion. (d) In a uniform circular motion, the speed continuously changes because the direction of motion changes. (e) A boy experiences a centrifugal force on his hand when he rotates a piece of stone tied at one end of a string. holding the other end in the hand.

A student is running at her top speed of 5.0 m s^(-1) , to catch a bus, which is stopped at the bus stop. When the student is still 40.0m from the bus, it starts to pull away, moving with a constant acceleration of 0.2 m s^(-2) . a For how much time and what distance does the student have to run at 5.0 m s^(-1) before she overtakes the bus? b. When she reached the bus, how fast was the bus travelling? c. Sketch an x-t graph for bothe the student and the bus. d. Teh equations uou used in part (a)to find the time have a second solution, corresponding to a later time for which the student and the bus are again at thesame place if they continue their specified motions. Explain the significance of this second solution. How fast is the bus travelling at this point? e. If the student s top speed is 3.5 m s^(-1), will she catch the bus? f. What is the minimum speed the student must have to just catch up with the bus?For what time and what distance dies she have to run in that case?

Five persons A, B, C, D & E are pulling a cart of mass 100kg on a smooth surface and cart is moving with acceleration 3m//s^2 in east direction. When person A' stops pulling, it moves with acceleration 1m//s^2 in the west direction. When person 'B' stops pulling, it moves with accele-ration 24m//s^2 in the north direction. The magnitude of acceleration of the cart when only A & B pull the cart keeping their directions same as the old direction is

ALLEN-NEWTONS LAWS OF MOTION-SWOE
  1. The friction coefficient between the board and the floor shown in figu...

    Text Solution

    |

  2. A man of mass 7.0 kg stands on a weighing scale in a lift which is mov...

    Text Solution

    |

  3. Explain why (a) A horse cannot pull a cart and run in empty space. ...

    Text Solution

    |

  4. Two bodies A and B of mass 5 kg and 10 kg contact with each other rest...

    Text Solution

    |

  5. A block of mass 1kg is at rest on a rough horizontal surface having co...

    Text Solution

    |

  6. Assuming the length of a chain to be L and coefficient of static frict...

    Text Solution

    |

  7. If the coefficient of friction between an insect and bowl is mu and th...

    Text Solution

    |

  8. A body of mass M is kept on a rough horizontal surface (friction coeff...

    Text Solution

    |

  9. A block rest on a rough inclined plane as shown in fig. A horizontal f...

    Text Solution

    |

  10. Two blocks of masses m(1)=1 kg and m(2)=2 kg are connected by a string...

    Text Solution

    |

  11. For shown situation draw a graph showing acceleration of A and B on y-...

    Text Solution

    |

  12. A block of mass m rests on a rough horizontl surface as shown in figur...

    Text Solution

    |

  13. A body of mass m rests on a horizontal floor with which it has a coeff...

    Text Solution

    |

  14. A block of 1 kg is stopped against a wall by applying a force F perpen...

    Text Solution

    |

  15. Two block A and B placed on a plane surface as shown in the figure. Th...

    Text Solution

    |

  16. Consider the figure shown here of a moving cart C. if the coefficient ...

    Text Solution

    |

  17. A block of mass kg lies on a horizontal surface in a truck· The coeff...

    Text Solution

    |

  18. Coefficient of friction between two block shown in figure is mu = 0.4....

    Text Solution

    |

  19. A horizontal force of 10 N is necessary to just hold a block stationar...

    Text Solution

    |

  20. Blocks A and B of masses 5 kg and 10kg are placed as shown in figure. ...

    Text Solution

    |