A point source of light is placed at the centre of curvature of a hemispherical surface The source emits a power of $24\, W$ The radius of curvature of hemisphere is $10\, cm$ and the inner surface is completely reflecting The force on the hemisphere due to the light falling on it is ______ $\times 10^{-8} N$
Correct Answer: 4
Solution and Explanation
Force =\(∫\;Pd\;A\;cosθ\)
= \(\frac{2I}{C}∫dA\;cosθ = \frac{2I}{C}πR^2= 2 \frac{p_o}{4\pi R^2}.\frac{\pi R^2}{C}\)
= \(\frac{p_0}{2C}=\frac{24}{2\times3\times10^8}=4×10^{−8}N\)
The correct answer is 4.
Top Questions on laws of motion
- Forces acting on 2 bodies of masses 2kg and 3kg are same. What is the ratio of their acceleration?
- KEAM - 2025
- Physics
- laws of motion
- Acceleration of the freely falling metal rod in a cycling ring?
- KEAM - 2025
- Physics
- laws of motion
- A stone is dropped from a height of 45 m. What is the time taken for the stone to reach the ground?
- VITEEE - 2025
- Physics
- laws of motion
- A force of \( 10 \, \text{N} \) acts on a body of mass \( 2 \, \text{kg} \). What is the acceleration of the body?
- VITEEE - 2025
- Physics
- laws of motion
- A body of mass 5 kg is moving with a velocity of 15 m/s. What is its momentum?
- VITEEE - 2025
- Physics
- laws of motion
Questions Asked in JEE Main exam
A molecule with the formula $ \text{A} \text{X}_2 \text{Y}_2 $ has all it's elements from p-block. Element A is rarest, monotomic, non-radioactive from its group and has the lowest ionization energy value among X and Y. Elements X and Y have first and second highest electronegativity values respectively among all the known elements. The shape of the molecule is:
- JEE Main - 2025
- Molecular Stability
A transition metal (M) among Mn, Cr, Co, and Fe has the highest standard electrode potential $ M^{n}/M^{n+1} $. It forms a metal complex of the type $[M \text{CN}]^{n+}$. The number of electrons present in the $ e $-orbital of the complex is ... ...
- JEE Main - 2025
- Transition Elements
Consider the following electrochemical cell at standard condition. $$ \text{Au(s) | QH}_2\text{ | QH}_X(0.01 M) \, \text{| Ag(1M) | Ag(s) } \, E_{\text{cell}} = +0.4V $$ The couple QH/Q represents quinhydrone electrode, the half cell reaction is given below: $$ \text{QH}_2 \rightarrow \text{Q} + 2e^- + 2H^+ \, E^\circ_{\text{QH}/\text{Q}} = +0.7V $$
- JEE Main - 2025
- Electrochemical Cells
0.1 mol of the following given antiviral compound (P) will weigh .........x $ 10^{-1} $ g.
- JEE Main - 2025
- Mole concept and Molar Masses
Consider the following equilibrium, $$ \text{CO(g)} + \text{H}_2\text{(g)} \rightleftharpoons \text{CH}_3\text{OH(g)} $$ 0.1 mol of CO along with a catalyst is present in a 2 dm$^3$ flask maintained at 500 K. Hydrogen is introduced into the flask until the pressure is 5 bar and 0.04 mol of CH$_3$OH is formed. The $ K_p $ is ...... x $ 10^7 $ (nearest integer).
Given: $ R = 0.08 \, \text{dm}^3 \, \text{bar} \, \text{K}^{-1} \, \text{mol}^{-1} $
Assume only methanol is formed as the product and the system follows ideal gas behavior.- JEE Main - 2025
- Equilibrium
Concepts Used:
Laws of Motion
The laws of motion, which are the keystone of classical mechanics, are three statements that defined the relationships between the forces acting on a body and its motion. They were first disclosed by English physicist and mathematician Isaac Newton.
Newton’s First Law of Motion
Newton’s 1st law states that a body at rest or uniform motion will continue to be at rest or uniform motion until and unless a net external force acts on it.
Newton’s Second Law of Motion
Newton's 2nd law of motion deals with the relation between force and acceleration. According to the second law of motion, the acceleration of an object as built by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.
Newton’s Third Law of Motion
Newton's 3rd law of motion states when a body applies a force on another body that there is an equal and opposite reaction for every action.