Physics 1 Marks Question

When the string breaks, the stone will move in the direction of the velocity at that instant. According to the first law of motion, the direction of velocity vector is tangential to the path of the stone at that instant. Hence, the stone will fly off tangentially from the instant the string breaks.

Force is being applied to overcome the force of friction. But as velocity of the car is constant, its acceleration, a = 0. Hence net force on the car F = ma = 0.

As the cork is floating on water, its weight is balanced by the up thrust due to water. Therefore, the net force on the cork is 0.

As the high speed electron in space is far away from all gravitating objects and free of electric and magnetic fields, the net force on electron is 0.

As the rain drop is filling with a constant speed, its acceleration, a = 0. Hence net force F = ma = 0.

As the kite is held stationery, in accordance with the first law of motion, the net force on the kite is 0.

Mass varies at every moment.

It is the reaction due to the surface on which the body moves. It acts perpendicular to the surface of contact.

Mass of a pebble = 0.05kg Since a pebble is thrown vertically upward, then it is accelerated downwards under the influence of a gravity pull. Net force on the pebble = mg = 0.05 × 10 = 0.5N vertically downward.

As the applied force increases, the static friction also increases and becomes equal to the applied force to make the object stationary. That is why static friction is called a self-adjusting force.

Sliding friction.

Friction, a tangential force provides the necessary torque to roll the body. This has to act opposite in the direction of motion to bring necessary motion.

Since earth rotates on its own axis and also revolves around the sun, there will be acceleration associated. So earth cannot be taken as inertial frame of reference.

The maximum height is reduced.

Any change in area, leads to only variation in the pressure experienced, but the force to be balanced remains the same.

Maximum static friction acting on body is known as limiting friction.

Remains constant.

Curved roads are generally banked so as to help in providing centripetal force needed to balance the centrifugal force, arising due to circular motion on the curved road.

Momentum transferred depends on mass and time in which it is brought to rest.

The electrostatic force of attraction between the nucleus and the electrons.

1. Electrostatic force.
2. Gravitational force.

They always act on the two bodies in contact and not on the same body.

It is dangerous because:When the passengers are standing in the bus, the centre of gravity of the system is raised and as such the whole system is in an unstable equilibrium.
When the running bus suddenly stops due to inertia of motion, the passengers fall forward on each other and this will cause a stampede.

To make use of a component of normal reaction to negotiate the curve.

The stone will move along the tangent at the point of breaking.

No, centripetal force always acts towards the centre.

Due to inertia.

If on applying same force on the bodies, same acceleration is produced, then their inertial masses are same.

It is easier to roll a barrel because at the time of rolling we require to apply a force in order to overcome rolling friction and value of rolling friction is much less than sliding friction.

The statement is correct. It is in accordance with Newton's second law of motion.

Friction depends on the hardness and smoothness of the surfaces in contact. So proper inflation is required.

Momentum of a body is defined as the product of its mass and the velocity with which it is moving Momentum = Mass × Velocity Momentum of a body depends upon it mass and the velocity.

Impulse

1kg wt. = 9.8 newton.

Zero.

No, because the frictional force is independent of area of contact.

No, force is not required to maintain a body in its state of uniform motion along a straight line.

The electrostatic force of attraction between the nucleus and the electrons.

Nuclear forces have the shortest range and gravitational forces have the longest range.

Yes. It rises up to limiting friction.

Coefficient of friction is a unit less and dimensionless term.

Person sitting in a moving bus in uniform motion fall forward when sudden break is applied. It is due to inertia of motion.

Force acting on a body is directly proportional to rate of change of linear momentum.

Rubber tyres are preferred because coefficient of friction between rubber and road is less than that between steel and road.

Force is being applied to overcome the force of friction. But as velocity of the car is constant, its acceleration, a = 0. Hence net force on the car F = ma = 0.

The angle is 180°, because force of friction always opposes the relative motion.

To reduce the force experienced, by increasing the time of contact.

To reduce the force experienced, by increasing the time of contact.

Weakest - Gravitational force. Strongest - Nuclear force.

Yes, if the external forces acting on the body can be represented in magnitude and direction by the sides of a closed polygon taken in the same order.

Inertia of a body is proportional to its mass.

As the cork is floating on water, its weight is balanced by the up thrust due to water. Therefore, the net force on the cork is 0.

To reduce friction under rolling.

Coefficient of friction is not affected as it depends only on material and nature of surfaces in contact.

Minimum angle of inclined plane with horizontal plane at which when a body is placed, just start sliding down is known as angle of repose.

The velocity of bullet being large, the bullet remains in contact with window glass for a shorter time than the stone of lesser velocity.

Nuclear force is the strongest of all forces.

A body having constant linear momentum then force acting on the body is equal to zero.

When we pull a lawn mover the vertical component of applied pull acts opposite to the weight of mover and it reduces the effective weight on the other hand. When the lawn mover is pushed vertical component of applied push adds to the weight of mover and therefore its effective weight is more than actual.

For finite change in linear momentum in short interval of time force acting on a body is inversely proportional to time.

A stone gains lesser momentum compared to a bullet. Window pane can create enough resistance to the stone, and not to the bullet.

When no external force acts on a body, there is no change in momentum or momentum will remain conserved.

Third law of Motion.

When a body is moving along a circular path, speed always remains constant and a centripetal force is acting on the body.

As the high speed electron in space is far away from all gravitating objects and free of electric and magnetic fields, the net force on electron is 0.

In a connected motion of two body, acceleration of both the bodies are equal.

The wings of aeroplane push the air backwards and the reaction of the air pushes the plane forward. At low altitudes, air is dense and as such the reaction of the air on plane is large.

This statement is wrong relative to any inertial frame of reference that we normally use (e.g., laboratory frame that is approximately inertial). The particle in circular motion is not in equilibrium, it has a centripetal acceleration. Centrifugal force does not exist relative to an inertial frame. The statement is correct relative to the (non-inertial) frame rotating with the particle.

The force of friction between the road and the tyres of car.

We have to overcome static friction, which is more than kinetic friction.

The upward thrust on a rocket depends on exhaust speed of the gases w.r.t. the rocket and rate at which mass of the exhaust gases escapes.

Vertically downward, since it was at rest at the highest point.

Jet planes use atmospheric oxygen for burning fuel but rockets carry their own fuel and oxygen and do not depend on atmospheric oxygen.

Impulse and change in momentum are along the same direction. Therefore, angle between these two vectors is zero degree.

Angle of friction which the resultant of limiting friction and normal reaction makes with the normal, is numerically equal to coefficient of static friction.

The carts with rubber tyres are easier to ply than those with iron types because the coefficient of friction between rubber and concrete is less than that between iron and the road.

From the kinetic energy of rocket.

To reduce the effect of any force by increasing the time of experience.

As the rain drop is filling with a constant speed, its acceleration, a = 0. Hence net force F = ma = 0.

Centrifugal force.

Frame of reference in which Newton's first law of motion is applicable is known as Inertial frame of reference.

The initial momentum of the boys holding the rope is zero. When one of the two pulls the other they move towards each other. To conserve momentum in the absence of external force the heavier of the two boys will move slower than the other.

Inertia of linear motion is measured by mass of the body, which is a scalar quantitiy.

Thread CD will break up if CD is pulled with the jerk because pull on thread CD is not transmitted from CD to AB by mass 2kg due to its inertia of rest.

Due to the accelerated nature of the frame, a pseudo force acts outward radially.

When lift moves with uniform speed acceleration is zero. Apparent weight = mg = 60 × 10 = 600N

The centripetal force will be directed towards the centre of the circle. This fact does not depend upon the sense of rotation of the particle.

The reading will be only 10kg wt, since one end will act as a rigid support.

Due to inertia of rest.

No change in speed, but change in direction is possible. Forces acting on a body in circular motion is an example.

Since, there are no near by stars to exert gravitational force on him and the small spaceship exert negligible gravitational attraction on him, the net force acting on the astronaut, once he is out of the spaceship is zero.

Running provides greater momentum which helps in jumping through a longer distance.

Yes, provided the vector sum of the forces acting upon the body is zero.

When the outer rail of a curved railway track is raised over the inner, the horizontal component of the normal reaction of the rails, provides the necessary centripetal force for the train to enable it moving along the curved path.

Zero, since there will be no reaction.

According to the Newton's second law of motion, F = ma, for given acceleration a, if m is large, F should be more i.e. greater force will be required to put a larger mass in motion.

Friction depends on the nature of the surface and so is highly varying and not dependable.

Newton's third law of motion.

Momentum, since no external force acts.

When the net force on it is zero.

Apparent weight increases, when the lift is accelerated upward and is same as original weight if it has uniform speed.

As the kite is held stationery, in accordance with the first law of motion, the net force on the kite is 0.

Object with smaller mass.

Change in momentum
= 0.15 × 12–(–0.15×12)
= 3.6 N s,
Impulse = 3.6 N s,
in the direction from the batsman to the bowler. This is an example where the force on the ball by the batsman and the time of contact of the ball and the bat are difficult to know, but the impulse is readily calculated.

Since there are no nearby stars to exert gravitational force on him and the small spaceship exerts negligible gravitational attraction on him, the net force acting on the astronaut, once he is out of the spaceship, is zero. By the first law of motion the acceleration of the astronaut is zero.