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
When a carpet is beaten with a stick, dust comes out of it. Explain.
Give the magnitude and direction of the net force acting on a drop of rain falling down with a constant speed.
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?
Find the acceleration produced by a force of 5 N acting on a mass of 10 kg.
Name the law involved in the following situation :
if there were no friction and no air resistance, then a moving bicycle would go on moving for ever.
The figure shows a light spring balance connected to two blocks of mass 20 kg each. The graduations in the balance measure the tension in the spring. (a) What is the reading of the balance? (b) Will the reading change if the balance is heavy, say 2.0 kg? (c) What will happen if the spring is light but the blocks have unequal masses?
Consider a book lying on a table. The weight of the book and the normal force by the table in the book are equal in magnitude and opposite in direction. Is this an example of Newton's third law?
A block of mass 10 kg is suspended from two light spring balances, as shown in the following figure.
In an imaginary atmosphere, the air exerts a small force F on any particle in the direction of the particle's motion. A particle of mass m projected upward takes time t1 in reaching the maximum height and t2 in the return journey to the original point. Then.
A reference frame attached to the earth
(a) is an inertial frame by definition
(b) cannot be an inertial frame because the earth is revolving around the sun
(c) is an inertial frame because Newton's laws are applicable in this frame
(d) cannot be an inertial frame because the earth is rotating about its axis.
The greater is the __________ the greater is the inertia of an object.
Give two examples of the following:
Inertia of motion
Match the following
| Column I | Column II |
| Newton’s I law | propulsion of a rocket |
| Newton’s II law | Stable equilibrium of a body |
| Newton’s III law | Law of force |
| Law of conservation of linear momentum | Flying nature of bird |
Newton's first law of motion describes ______.
A body of mass 10 kg is acted upon by two perpendicular forces, 6 N and 8 N. The resultant acceleration of the body is ______.
- 1 m s–2 at an angle of tan−1 `(4/3)` w.r.t 6 N force.
- 0.2 m s–2 at an angle of tan−1 `(4/3)` w.r.t 6 N force.
- 1 m s–2 at an angle of tan−1 `(3/4)` w.r.t 8 N force.
- 0.2 m s–2 at an angle of tan−1 `(3/4)` w.r.t 8 N force.
In the above given problem if the lower thread is pulled with a jerk, what happens?
What is the significance of Newton’s first law?
If the net force on an object is zero, what happens?
