The potential energy in joules of a particle of mass $1\, kg$ moving in a plane is given by $U = 3x + 4y$, the position coordinates of the point being $x$ and $y$, measured in metres. If the particle is initially at rest at $(6,4)$, then
its acceleration is of magnitude $5\, m/s^2$
its speed when it crosses the $y$ -axis is $10\, m/s$
it crosses the $ y$ -axis $(x = 0)$ at $y = -4$
All of the above
A block of mass $1\,kg$ slides on a rough horizontal surface. If the speed of the block decreases from $10\,m/s$ to $8\,m/s$ , the thermal energy developed in this process .................. $\mathrm{J}$
A rocket accelerates straight up by ejecting gas downwards. In a small time interval $\Delta t$, it ejects a gas of mass $\Delta m$ at a relative speed $u$. Calculate $KE$ of the entire system at $t + \Delta t$ and $t$ and show that the device that ejects gas does work $=(\frac {1}{2})\Delta mu^2$ in this time interval (negative gravity).
A ball of mass $0.2\ kg$ is thrown vertically upwards by applying a force by hand. If the hand moves $0.2\ m$ while applying the force and the ball goes upto $2\ m$ height further, find the magnitude of the force .......... $N$ .(consider $g = 10\; m/s^2$)
A particle is projected vertically upwards with a speed of $16\ m/s$ , after some time , when it again passes through the point of projection, its speed is found to be $8\ m/s$ . It is known that the work done by air resistance is same during upward and downward motion. Then the maximum height attained by the particle is ...................... $\mathrm{m}$ ( $g$ = $10\ m/s^2$ )
A spherical ball of mass $20\, kg$ is stationary at the top of a hill of height $100 \,m$. It slides down a smooth surface to the ground, then climbs up another hill of height $30 \,m$ and finally slides down to a horizontal base at a height of $20 \,m$ above the ground. The velocity attained by the ball is ............... $\mathrm{m} / \mathrm{s}$