Normal Force

Q.

A man getting down a running bus falls forward because

1. Due to inertia of rest, road is left behind and man reaches forward

2. Due to inertia of motion upper part of the body continues to be in motion in forward direction while feet come to rest as soon as they touch the road

3. He leans forward as a matter of habit

4. Of the combined effect of all the three factors stated in (a), (b) and (c)

Q.

How does Newtons 3rd law apply to rockets?

Q.

Which of the following is not a derived quantity?

1. The floor area of a room

2. The height of a room

3. The volume of air in a room

4. The weight of air in a room

Q. The molecule at the surface of the liquid feels the net force in the________ direction.

1. Upward direction
2. Downward direction
3. Right direction
4. Net force is zero.

Q.

A man having a box on his head, climbs up a slope and another man having an identical box walks the same distance on a levelled road. Who does more work against the force of gravity and why?

Q.

A body of mass 1.0 kg initially at rest is moved by a horizontal force of 0.5 N on a smooth table. Calculate the work done by the force in 10 s and show that it is equal to the change
in K.E. of the body.

Q.

What is the amount of work done by a weight-lifter in holding a weight of 100 kg on his shoulders for 40 s?

Q. A bird is in a wire cage hanging from a spring balance.The reading of the balance is taken when the bird is flyingabout in the cage, and when the bird is at rest in the cage. The first reading will be pess than the second.WHY

Q.

if a stationary bus was suddenly speed up passenger are thrown in backward direction why is it so

If it is because of inertia then which type of inertia

Q.

If we are seated inside a Bus at rest and the Bus suddenly starts, we tend to fall back. Why ?

Q.

An object weighs 20 newtons when measured on the surface of the earth. What is its weight when measured on the surface of the moon?

Q. A horizontal force of 5N act on a block of mass 10 kg kept on a rough horizontal surface. The coefficient of friction between the block and the rough surface is 0.3. Find the magnitude of frictional force acting between them, (g = 10 m/s²)

Q.

Why Spring Force Is Non Impulsive

Q. Two cubes of masses 3 g and 6 g and sides of length $2\text{cm}$ and $3\text{cm}$ respectively are placed on a smooth table as shown in the figure. Calculate the pressure experienced by the table due to the system of boxes. [Take $g=10m/s^2]$

1. 100 Pa
2. 60 Pa
3. 120 Pa
4. 80 Pa

Q. When a horizontal force P acts on a cart of mass 20KG , it moves with a uniform velocity on a horizontal floor. When a force of 1.2P acts on the cart , it moves with an acceleration of 0.05m/s² .Find the valve of P?

Q. A box of mass 50kg is kept on a horizontal floor.when it is pushed by a horizontal force H, it moves with a constant velocity.If it is pushed by a horizontal force 1.5H, it moves with an acceleration of 0.1metre/ second square.Find the value of H

Q.

When will the force of friction acting on a moving car be more -on rainy day or sunny day

Q. A spring balance reads 200gF when carrying a lump of lead in air. If the lead isnow immersed with half of its volume in brine solution, what will be the new reading of the spring balance? Specific gravity of lead and brine are 11.4 and 1.1 respectively.

Q.

Why are the cutting edges of Pliers smaller than the cutting edges of Scissors?

Q.

A stone of 2 kg is thrown with a velocity of 20 ${ms}^{-1}$ across the frozen surface of a lake and comes to rest after travelling a distance of 100 m. Calculate the frictional force between the stone and the ice.

1. 2N

2. (-) 2 N

3. 3N

4. 4N

Q.

Two point charges + q and -2q are placed at the vertices B and C of an equilateral triangle ABC of side a as given in the figure. Obtain the expression for the direction of the resultant electric field at the vertex A due to these two charges.

1. $\alpha ={20}^0$
2. $\alpha ={90}^0$
3. $\alpha ={70}^0$
4. $\alpha ={30}^0$

Q.

Estimate the mass of the moon if the value of acceleration due to gravity on its surface is 1.6 ms^-2 and its radius is 1800 km. Given that G = 6.67 x 10^-11 Nm² kg^-2.

Q.

Calculate the distance through which a tonga moves when the horse applies a force of $250N$ and the work done is $6250J$.

Q. The weight of a boy on the surface of the earth is 300 N. What will be his mass? { take $g=10m/s^2$}

1. $30\text{kg}$
2. $200\text{kg}$
3. $20\text{kg}$
4. $300\text{kg}$

Q.

A man of mass $50kg$ is standing in an elevator. If the elevator is moving up with an acceleration $\frac{g}{3}$ then what is the work one by normal reaction of the floor of the elevator on the man when elevator moves by a distance 12m? $\left(g=10m/s^2\right)$

1. 8000 J

2. 6000 J

3. 4000 J

4. 2000 J

Q. of sound stops as soon as the vibration of the source stops.

1. Production
2. Propagation
3. Hearing

Q.

How do space vehicles apply action and reaction forces to blast off?

Q. When a horizontal force P acts on a cart of mass 20KG , it moves with a uniform velocity on a horizontal floor. When a force of 1.2P acts on the cart , it moves with an acceleration of 0.05m/s² .Find the valve of P?

Q. In Fig. 1.35, a uniform bar of length l m is supported at its end and loaded by a weight W kgf at its middle. In equilibrium, find the reactions $R_1$ and $R_2$ at the ends.

Q. The Force of $500N$ acts on body of mass $5kg$ for $10sec$. The change in momentum of body is

1. $1000N$
2. $25000N$
3. $10000N$
4. $5000N$