Newton’s Laws of Motion Physics - Newton’s Laws of Motion

The apparent weight of an object increases in an elevator while accelerating upward. A moongphaliwala sells his moongphali using a beam balance in an elevator. Will he gain more if the elevator is accelerating up?

A block of mass 0.2kg is suspended from the ceiling by a light string. A second block of mass 0.3kg is suspended from the first block through another string. Find the tensions in the two strings. Take g = 10m/s².

A person drops a coin. Describe the path of the coin as seen by the person if he is in:

1. A car moving at constant velocity.
2. In a freely falling elevator.

A particle of mass 0.3kg is subjected to a force F = -kx with k = 15N/m. What will be its initial acceleration if it is released from a point x = 20cm?

If you jump barefooted on a hard surface, your legs get injured. But they are not injured if you jump on a soft surface like sand or pillow. Explain.

Calculate the tension in the string shown in figure. The pulley and the string are light and all surfaces are frictionless. Take g = 10m/s².

Two blocks of equal mass m are tied to each other through a light string. One of the blocks is pulled along the line joining them with a constant force F. Find the tension in the string joining the blocks.

A monkey is climbing on a rope that goes over a smooth light pulley and supports a block of equal mass at the other end figure. Show that whatever force the monkey exerts on the rope, the monkey and the blockmove in the same direction with equal acceleration. If initially both were at rest, their separation will not change as time passes.

A monkey of mass 15kg is climbing on a rope with one end fixed to the ceiling. If it wishes to go up with an acceleration of 1m/s², how much force should it apply to the rope? If the rope is 5m long and the monkey starts from rest, how much time will it take to reach the ceiling?

Raindrops of radius 1mm and mass 4mg are falling with a speed of 30m/s on the head of a bald person. The drops splash on the head and come to rest. Assuming equivalently that the drops cover a distance equal to their radii on the head, estimate the force exerted by each drop on the head.

Two blocks A and B of mass m_A and m_B respectively are kept in contact on a frictionless table. The experimenter pushes the block A from behind so that the blocks accelerate. If the block A exerts a force F on the block B, what is the force exerted by the experimenter on A?

The acceleration of a particle is zero as measured from an inertial frame of reference. Can we conclude that no force acts on the particle?

Consider a book lying on a table. The weight of the book and the normal force by the table on the book are equal in magnitude and opposite in direction. Is this an example of Newton's third law?

An object is placed far away from all the objects that can exert force on it. A frame of reference is constructed by taking the origin and axes fixed in this object. Will the frame be necessarily inertial?

A man has fallen into a ditch of width d and two of his friends are slowly pulling him out using a light rope and two fixed pulleys as shown in figure. Show that the force (assumed equal for both the friends) exerted by each friend on the road increases as the man moves up. Find the force when the man is at a depth h.

In a TV picture tube electrons are ejected from the cathode with negligible speed and reach a velocity of 5 × 10⁶m/s in travelling one centimeter. Assuming straight line motion, find the constant force exerted on the electron. The mass of the electron is 9.1 × 10^-31kg.

A person is standing on a weighing machine placed on the floor of an elevator. The elevator starts going up with some acceleration, moves with uniform velocity for a while and finally decelerates to stop. The maximum and the minimum weights recorded are 72kg and 60kg. Assuming that the magnitudes of the acceleration and the deceleration are the same, find:

1. The true weight of the person.
2. The magnitude of the acceleration. Take g = 9.9m/s².

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Suppose you are running fast in a field when you suddendly find a snake in front of you. You stop quickly. Which force is responsible for your deceleration?

Find the acceleration of the blocks A and B in the three situations shown in figure.

Figure shows a light spring balance connected to two blocks of mass 20kg each. The graduations in the balance measure the tension in the spring.

1. What is the reading of the balance?
2. Will the reading change if the balance is heavy, say 2.0kg?
3. What will happen if the spring is light but the blocks have unequal masses?

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Consider the situation shown in figure. Both the pulleys and the string are light and all the surfaces are frictionless.

1. Find the acceleration of the mass M.
2. Find the tension in the string.
3. Calculate the force exerted by the clamp on the pulley A in the figure.

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A pendulum bob of mass 50g is suspended from the ceiling of an elevator. Find the tension in the string if the elevator:

1. Goes up with acceleration 1.2m/s².
2. Goes up with deceleration 1.2m/s².
3. Goes up with uniform velocity.
4. Goes down with acceleration 1.2m/s².
5. Goes down with deceleration 1.2m/s².
6. Goes down with uniform velocity.

Find the acceleration of the block of mass M in the situation shown in figure. All the surfaces are frictionless and the pulleys and the string are light.