Science (English Medium) Class 11 - CBSE Question Bank Solutions for Physics

For the one-dimensional motion, described by x = t – sint

1. x (t) > 0 for all t > 0.
2. v (t) > 0 for all t > 0.
3. a (t) > 0 for all t > 0.
4. v (t) lies between 0 and 2.

A spring with one end attached to a mass and the other to a rigid support is stretched and released.

1. Magnitude of acceleration, when just released is maximum.
2. Magnitude of acceleration, when at equilibrium position, is maximum.
3. Speed is maximum when mass is at equilibrium position.
4. Magnitude of displacement is always maximum whenever speed is minimum.

A ball is bouncing elastically with a speed 1 m/s between walls of a railway compartment of size 10 m in a direction perpendicular to walls. The train is moving at a constant velocity of 10 m/s parallel to the direction of motion of the ball. As seen from the ground ______.

1. the direction of motion of the ball changes every 10 seconds.
2. speed of ball changes every 10 seconds.
3. average speed of ball over any 20 second interval is fixed.
4. the acceleration of ball is the same as from the train.

Give examples of a one-dimensional motion where

1. the particle moving along positive x-direction comes to rest periodically and moves forward.
2. the particle moving along positive x-direction comes to rest periodically and moves backward.

A motor car moving at a speed of 72 km/h can not come to a stop in less than 3.0 s while for a truck this time interval is 5.0 s. On a highway the car is behind the truck both moving at 72 km/h. The truck gives a signal that it is going to stop at emergency. At what distance the car should be from the truck so that it does not bump into (collide with) the truck. Human response time is 0.5 s.

A particle falling vertically from a height hits a plane surface inclined to horizontal at an angle θ with speed vo and rebounds elastically (Figure). Find the distance along the plane where if will hit second time.

A man wants to reach from A to the opposite corner of the square C (Figure). The sides of the square are 100 m. A central square of 50 m × 50 m is filled with sand. Outside this square, he can walk at a speed 1 m/s. In the central square, he can walk only at a speed of v m/s (v < 1). What is smallest value of v for which he can reach faster via a straight path through the sand than any path in the square outside the sand?

A ball is travelling with uniform translatory motion. This means that ______.

Why are porcelain objects wrapped in paper or straw before packing for transportation?

The displacement vector of a particle of mass m is given by `r(t) = hati` A cos ωt + `hatj` B sin ωt. Show that the trajectory is an ellipse.

The displacement vector of a particle of mass m is given by r(t) = `hati` A cos ωt + `hatj` B sin ωt. Show that F = − mω²r.

A ballon has 5.0 g mole of helium at 7°C. Calculate

1. the number of atoms of helium in the balloon
2. the total internal energy of the system.

Calculate the number of degrees of freedom of molecules of hydrogen in 1 cc of hydrogen gas at NTP.

Which of the following is the most precise device for measuring length:

1. a vernier callipers with 20 divisions on the sliding scale
2. a screw gauge of pitch 1 mm and 100 divisions on the circular scale
3. an optical instrument that can measure length to within a wavelength of light?

In the following examples of motion, can the body be considered approximately a point object:

A railway carriage moving without jerks between two stations.

A drunkard walking in a narrow lane takes 5 steps forward and 3 steps backward, followed again by 5 steps forward and 3 steps backward, and so on. Each step is 1 m long and requires 1 s. Plot the x-t graph of his motion. Determine graphically and otherwise how long the drunkard takes to fall in a pit 13 m away from the start.

Read the statement below carefully and state, with reason and example, if it is true or false:

A particle in one-dimensional motion with zero speed at an instant may have non-zero acceleration at that instant

Explain clearly, with examples, the distinction between:

1. magnitude of displacement (sometimes called distance) over an interval of time, and the total length of path covered by a particle over the same interval.
2. magnitude of average velocity over an interval of time, and the average speed over the same interval. [Average speed of a particle over an interval of time is defined as the total path length divided by the time interval]. Show in both (a) and (b) that the second quantity is either greater than or equal to the first. When is the equality sign true ? [For simplicity, consider one-dimensional motion only].

Look at the graph carefully and state, with reason, that this cannot possibly represent the one-dimensional motion of a particle.

Rain is falling vertically with a speed of 30 m s^–1. A woman rides a bicycle with a speed of 10 m s^–1in the north to south direction. What is the direction in which she should hold her umbrella?