Advertisements
Advertisements
Question
The force exerted by the floor of an elevator on the foot of a person is more than the weight of the person if the elevator is
(a) going up and slowing down
(b) going up and speeding up
(c) going down and slowing down
(d) going down and speeding up
Advertisements
Solution
(b) going up and speeding up
(c) going down and slowing down
It means normal force exerted by the floor of the elevator on the person is greater that the weight of the person.
i.e. N > mg
(i) Going up and speeding up:
aeff = g + a
N = maeff = mg + ma (N > mg)
(ii) Going down and speeding up:
aeff = g – a
N = mg – ma (N < mg)
(iii) Going down and slowing down:
aeff = g – (–a) = g + a
N = mg + ma (N > mg)
(iv) Going up and slowing down:
aeff = g – a
N = mg – ma (N < mg)
APPEARS IN
RELATED QUESTIONS
The driver of a three-wheeler moving with a speed of 36 km/h sees a child standing in the middle of the road and brings his vehicle to rest in 4.0 s just in time to save the child. What is the average retarding force on the vehicle? The mass of the three-wheeler is 400 kg and the mass of the driver is 65 kg.
If 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?
Fill in the following blank with suitable word :
Newton’s first law of motion is also called Galileo’s law of ………………………
It is sometimes heard that the inertial frame of reference is only an ideal concept and no such inertial frame actually exists. Comment.
A block of 2 kg is suspended from a ceiling by a massless spring of spring constant k = 100 N/m. What is the elongation of the spring? If another 1 kg is added to the block, what would be the further elongation?
When a train starts, the head of a standing passenger seems to be pushed backward. Analyse the situation from the ground frame. Does it really go backward? Coming back to the train frame, how do you explain the backward movement of the head on the basis of Newton's laws?
State and explain the law of inertia (or Newton's first law of motion).
Give qualitative definition of force on the basic of Newton's first law of motion.
Explain the following :
After alighting from a moving bus , one has to run for some distance in the direction of bus in order to avoid falling .
Derive the relation between newton and dyne.
Name the scientist who first stated the law of inertia.
If a 5 N and a 15 N forces are acting opposite to one another. Find the resultant force and the direction of action of the resultant force.
A car of mass m starts from rest and acquires a velocity along east `v = vhati (v > 0)` in two seconds. Assuming the car moves with uniform acceleration, the force exerted on the car is ______.
In a legend, the hero-kid kicked a toy pig so that it is projected with a speed greater than that of its cry. If the weight of the toy pig is assumed to be 5 kg and the time of contact 0.01 sec., the force with which the hero-kid kicked him was ______.
(Speed of cry = 330 m/s)
A force F is applied to the initially stationary cart. The variation of force with time is shown in the figure. The speed of the cart at t = 5 sec is ______.
What is the significance of Newton’s first law?
When does an object accelerate?
An insect is at the bottom of a hemispherical ditch of radius 1 m. It crawls up the ditch but starts slipping after it is at height h from the bottom. If the coefficient of friction between the ground and the insect is 0.75, then h is ______. (g = 10 ms−2)
