Question

3. A conservative force of (-3i) N acts on a body of
mass 3 kg. The change in potential energy of the
body due to the force, when it undergoes a
displacement 61 m is
(1) 21 J
(2) 18 J
Wers
(3) 19 J
(4) 15 J
A small ball of mass 10 kg is moving with speed
4 m/s collides elastically with another ball of mass
6 kg at rest. If the collision is head-on, then the
respective speeds of the balls after the collision
will be​

Answer 1

3). 18 J

4). 20m/s

Explanation:

3). Given,

Force(F) = -3i

Displacement(S) = 6i

We know,

Work Done = -Δu

To find the change in potential energy,

= F * S

= -3i * 6i

∵ -18 J or 18J

4). Given,

Mass of ball = 10kg

Speed = 4m/s

Mass of the other ball at rest = 6kg

so,

$V_{2}$ = $(\frac{2m_{1} }{m_{1} + m_{2} } )u_{1}$ + $\frac{(m_{1} - m_{2})}{(m_{1} + m_{2})} u_{2}$

= {(2 * 10)/(10 + 6)}4 + {(10 - 6)/(10 + 6)}$u_{2}$

= 5 + $u_{2}$/4

∵ $u_{2}$ = 20m/s

Learn more: Potential energy

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