Science (English Medium) कक्षा ११ - CBSE Question Bank Solutions

A man runs across the roof-top of a tall building and jumps horizontally with the hope of landing on the roof of the next building which is of a lower height than the first. If his speed is 9 m/s, the (horizontal) distance between the two buildings is 10 m and the height difference is 9 m, will he be able to land on the next building? (take g = 10 m/s²)

The velocity-displacement graph of a particle is shown in figure.

1. Write the relation between v and x.
2. Obtain the relation between acceleration and displacement and plot it.

Calculate the work done by a car against gravity in moving along a straight horizontal road. The mass of the car is 400 kg and the distance moved is 2 m.

An adult weighing 600 N raises the centre of gravity of his body by 0.25 m while taking each step of 1 m length in jogging. If he jogs for 6 km, calculate the energy utilised by him in jogging assuming that there is no energy loss due to friction of ground and air. Assuming that the body of the adult is capable of converting 10% of energy intake in the form of food, calculate the energy equivalents of food that would be required to compensate energy utilised for jogging.

A wheel in uniform motion about an axis passing through its centre and perpendicular to its plane is considered to be in mechanical (translational plus rotational) equilibrium because no net external force or torque is required to sustain its motion. However, the particles that constitute the wheel do experience a centripetal acceleration directed towards the centre. How do you reconcile this fact with the wheel being in equilibrium? How would you set a half-wheel into uniform motion about an axis passing through the centre of mass of the wheel and perpendicular to its plane? Will you require external forces to sustain the motion?

A disc of radius R is rotating with an angular speed ωo about a horizontal axis. It is placed on a horizontal table. The coefficient of kinetic friction is µ_k.

1. What was the velocity of its centre of mass before being brought in contact with the table?
2. What happens to the linear velocity of a point on its rim when placed in contact with the table?
3. What happens to the linear speed of the centre of mass when disc is placed in contact with the table?
4. Which force is responsible for the effects in (b) and (c).
5. What condition should be satisfied for rolling to begin?
6. Calculate the time taken for the rolling to begin.

Both earth and moon are subject to the gravitational force of the sun. As observed from the sun, the orbit of the moon ______.

In our solar system, the inter-planetary region has chunks of matter (much smaller in size compared to planets) called asteroids. They ______.

If the sun and the planets carried huge amounts of opposite charges ______.

1. all three of Kepler’s laws would still be valid.
2. only the third law will be valid.
3. the second law will not change.
4. the first law will still be valid.

If the sun and the planets carried huge amounts of opposite charges ______.

1. all three of Kepler’s laws would still be valid.
2. only the third law will be valid.
3. the second law will not change.
4. the first law will still be valid.

Supposing Newton’s law of gravitation for gravitation forces F₁ and F₂ between two masses m₁ and m₂ at positions r₁ and r₂ read F₁ = – F₂ = `- r_12/r_12^3 GM_0^2 ((m_1m_2)/M_0^2)^n` where M₀ is a constant of dimension of mass r₁₂ = r₁ – r₂ and n is a number. in such a case.

1. the acceleration due to gravity on earth will be different for different objects.
2. none of the three laws of Kepler will be valid.
3. only the third law will become invalid.
4. for n negative, an object lighter than water will sink in water.

The centre of mass of an extended body on the surface of the earth and its centre of gravity ______.

1. are always at the same point for any size of the body.
2. are always at the same point only for spherical bodies.
3. can never be at the same point.
4. is close to each other for objects, say of sizes less than 100 m.
5. both can change if the object is taken deep inside the earth.

Give one example each of central force and non-central force.

Draw areal velocity versus time graph for mars.

What is the direction of areal velocity of the earth around the sun?

Out of aphelion and perihelion, where is the speed of the earth more and why?

A star like the sun has several bodies moving around it at different distances. Consider that all of them are moving in circular orbits. Let r be the distance of the body from the centre of the star and let its linear velocity be v, angular velocity ω, kinetic energy K, gravitational potential energy U, total energy E and angular momentum l. As the radius r of the orbit increases, determine which of the above quantities increase and which ones decrease.

Earth’s orbit is an ellipse with eccentricity 0.0167. Thus, earth’s distance from the sun and speed as it moves around the sun varies from day to day. This means that the length of the solar day is not constant through the year. Assume that earth’s spin axis is normal to its orbital plane and find out the length of the shortest and the longest day. A day should be taken from noon to noon. Does this explain variation of length of the day during the year?

A satellite is in an elliptic orbit around the earth with aphelion of 6R and perihelion of 2 R where R= 6400 km is the radius of the earth. Find eccentricity of the orbit. Find the velocity of the satellite at apogee and perigee. What should be done if this satellite has to be transferred to a circular orbit of radius 6R ?

[G = 6.67 × 10^–11 SI units and M = 6 × 10²⁴ kg]

Pressure is a scalar quantity because ______.

1. it is the ratio of force to area and both force and area are vectors.
2. it is the ratio of the magnitude of the force to area.
3. it is the ratio of the component of the force normal to the area.
4. it does not depend on the size of the area chosen.