Advertisements
Advertisements
Question
Explain why a horse cannot pull a cart and run in empty space.
Solution
In attempting to pull a cart, a horse applies a backward force at an angle against the ground. The ground reacts with an equal force in the opposite direction, acting on the horse’s feet. The forward component of this reaction force moves the cart. In a vacuum, such as empty space, no such reaction force exists, preventing the horse from pulling the cart and running.Therefore, a horse cannot pull a cart and run in empty space.
APPEARS IN
RELATED QUESTIONS
One end of a string of length l is connected to a particle of mass m and the other to a small peg on a smooth horizontal table. If the particle moves in a circle with speed the net force on the particle (directed towards the centre) is:
T is the tension in the string.
A body of mass 5 kg is acted upon by two perpendicular forces 8 N and 6 N. Give the magnitude and direction of the acceleration of the body.
A truck starts from rest and accelerates uniformly at 2.0 m s–2. At t = 10 s, a stone is dropped by a person standing on the top of the truck (6 m high from the ground).
- What are the velocity, and
- acceleration of the stone at t = 11?(Neglect air resistance.)
In Figure, the co-efficient of friction between the floor and the body B is 0.1. The co-efficient of friction between the bodies B and A is 0.2. A force F is applied as shown on B. The mass of A is m /2 and of B is m. Which of the following statements are true?
- The bodies will move together if F = 0.25 mg.
- The body A will slip with respect to B if F = 0.5 mg.
- The bodies will move together if F = 0.5 mg.
- The bodies will be at rest if F = 0.1 mg.
- The maximum value of F for which the two bodies will move together is 0.45 mg.
Mass m1 moves on a slope making an angle θ with the horizontal and is attached to mass m2 by a string passing over a frictionless pulley as shown in figure. The coefficient of friction between m1 and the sloping surface is µ.
- If m2 > m1 sin θ, the body will move up the plane.
- If m2 > m1 (sin θ + µ cos θ), the body will move up the plane.
- If m2 < m1 (sin θ + µ cos θ), the body will move up the plane.
- If m2 < m1 (sin θ − µ cos θ), the body will move down the plane.
Why are mountain roads generally made winding upwards rather than going straight up?
Two masses of 5 kg and 3 kg are suspended with help of massless inextensible strings as shown in figure. Calculate T1 and T2 when whole system is going upwards with acceleration = 2 ms2 (use g = 9.8 ms–2).
A block of mass M is held against a rough vertical wall by pressing it with a finger. If the coefficient of friction between the block and the wall is µ and the acceleration due to gravity is g, calculate the minimum force required to be applied by the finger to hold the block against the wall?
A person in an elevator accelerating upwards with an acceleration of 2 ms–2, tosses a coin vertically upwards with a speed of 20 ms1. After how much time will the coin fall back into his hand? ( g = 10 ms–2)
A rectangular box lies on a rough inclined surface. The co-efficient of friction between the surface and the box is µ. Let the mass of the box be m.
- At what angle of inclination θ of the plane to the horizontal will the box just start to slide down the plane?
- What is the force acting on the box down the plane, if the angle of inclination of the plane is increased to α > θ ?
- What is the force needed to be applied upwards along the plane to make the box either remain stationary or just move up with uniform speed?
- What is the force needed to be applied upwards along the plane to make the box move up the plane with acceleration a?
