Q11 (a),(b),(c) and Q12 (b)
11.(a) The leaves would get detached if the force applied is greater than the force that holds those leaves attached to the tree. Every shake of the tree would not result in falling of leaves but only those that generate greater force than the force that holds the leaves to the tree.
(b)
Because in this way he increases the time of catch to reduce the momentum of the ball to zero.
As, force = change in momentum/time
Therefore player has to apply a smaller force against the ball to stop it. The ball in turn exert a smaller force on his hand and thus the hands are not injured.
(c) By Newton's Third Law, the force at which the water is forced out of the hose has to equal the force which the water pushes back. The principles also apply to momentum, the amount (mass) of water being shot out (velocity) produces a recoil on the hose. To stop the hose from moving, the firefighter has to supply his own force on the hose, and given how much water and how power it is being shot out of the hose, the firefighter must exert a large quantity of force to counter the hose's recoil.
12. (b) Here mass = m = 10 kg
So weight of the body = W = mg = 10 x 9.8 = 98 N
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