Question -
Answer -
(a) In order to pull a cart, a horse pushes theground backward with some force. The ground in turn exerts an equal andopposite reaction force upon the feet of the horse. This reaction force causesthe horse to move forward.
Anempty space is devoid of any such reaction force. Therefore, a horse cannotpull a cart and run in empty space.
(b) When a speeding bus stops suddenly, thelower portion of a passenger’s body, which is in contact with the seat,suddenly comes to rest. However, the upper portion tends to remain in motion(as per the first law of motion). As a result, the passenger’s upper body isthrown forward in the direction in which the bus was moving.
(c) While pulling a lawn mower, a force at anangle θ is applied on it, as shown in the following figure.
Thevertical component of this applied force acts upward. This reduces theeffective weight of the mower.
On the other hand, while pushing a lawnmower, a force at an angle θ is applied on it, as shown in thefollowing figure.
Inthis case, the vertical component of the applied force acts in the direction ofthe weight of the mower. This increases the effective weight of the mower.
Sincethe effective weight of the lawn mower is lesser in the first case, pulling thelawn mower is easier than pushing it.
(d) According to Newton’s second law of motion,we have the equation of motion:
Where,
F = Stopping force experienced by thecricketer as he catches the ball
m = Mass of the ball
Δt = Time of impact of the ballwith the hand
It can be inferred from equation (i)that the impact force is inversely proportional to the impact time, i.e.,
Equation (ii) shows that the forceexperienced by the cricketer decreases if the time of impact increases and viceversa.
Whiletaking a catch, a cricketer moves his hand backward so as to increase the timeof impact (Δt). This is turn results in the decrease in the stoppingforce, thereby preventing the hands of the cricketer from getting hurt.