NEET 2019
For the following questions answer them individually
A disc of radius 2 m and mass 100 kg rolls on a horizontal floor. Its centre of mass has speed of 20 cm/s. How much work is needed to stop it ?
A block of mass 10 kg is in contact against the inner wall of a hollow cylindrical drum of radius 1m. The coefficient of friction between the block and the inner wall of the cylinder is 0.1. The minimum angular velocity needed for the cylinder to keep the block stationary when the cylinder is vertical and rotating about its axis, will be : $$(g = 10 m/s^2)$$
In an experiment, the percentage of error occurred in the measurement of physical quantities A, B, C and D are 1%, 2%, 3% and 4% respectively. Then the maximum percentage of error in the measurement X, where $$X = \frac {A^2 B^{\frac{1}{2}}}{C^{\frac{1}{3}}D^3},$$ will be:
A copper rod of 88 cm and an aluminium rod of unknown length have their increase in length independent of increase in temperature. The length of aluminium rod is : $$(\alpha_{Cu}) =1.7 \times 10^{-5} K^{-1} and \alpha_{Al} = 2.2 \times 10^{-5} K^{-1})$$
A force F = 20 + 10y acts on a particle in y-direction where F is in newton and y in meter. Work done by this force to move the particle from y = O to y = 1 m is:
An electron is accelerated through a potential difference of 10,000 V. Its de Broglie wavelength is, (nearly) : $$(m_e = 9 \times 10^{-31} kg)$$
The work done to raise a mass m from the surface of the earth to a height h, which is equal to the radius of the earth, is:
At a point A on the earth’s surface the angle of dip, $$\delta = + 25^\circ$$. At a point B on the earth’s surface the angle of dip, $$\delta = - 25^\circ$$ We can interpret that:
A soap bubble, having radius of 1 mm,is blown from a detergent solution having a surface tension of $$2.5 \times 10^{-2}N/m.$$ The pressure inside the bubble equals at a point $$Z_0$$, below the free surface of water Taking $$g = 10 m/s^2$$, density of water $$= 10^3 kg/m^3$$, the value of $$Z_0$$ is :
