Question 305: Work, Energy and Power & Circular Motion

Question

A cricket ball of mass 0.15 kg is thrown
vertically up by a bowling machine so that it
rises to a maximum height of 20 m after leaving
the machine. If the part pushing the ball applies
a constant force F on the ball and moves
horizontally a distance of 0.2 m while launching
the ball, the value of F (in N) is (g = 10 ms
–2
)
____.

Accepted Answer

Initial velocity, v = $$\sqrt {2gh} $$
= $$\sqrt {2 	imes 10 	imes 20} $$
= 20 m/s
Now work done by the machine,
W
F
= $$\Delta $$k
$$ \Rightarrow $$ F.d = $$\Delta $$k
$$ \Rightarrow $$ F = $${{\Delta k} \over d}$$
= $${{{1 \over 2} 	imes 0.15 	imes 400 - 0} \over {0.2}}$$
= 150 N

Work, Energy and Power & Circular Motion

Integer / Numeric Answer Type