Chapter 4 – Turning Effect of Forces
A force of 150 N can loosen a nut when applied at the end of a spanner 10cm long.
F = 150 N
L = 10 cm = 0.1 m
So
t = F x L
t = 150 x 0.1
t = 15 Nm
What should be the length of the spanner to loosen the same nut with a 60 N force?
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t = F x L
15 = 60 x L
L = 15 / 60
L = 0.25 m
L = 25 cm
How much force would be sufficient to loosen it with a 6 cm long spanner?
Ans: As
L = 6 cm = 0.06 m
t = F x L
15 = F x 0.06 m
L = 15 / 0.06
L = 250 N
Can a smart child play with a fat child on the see-saw? Explain how?
Ans: Yes, Fat child can play with smart child by adjusting the moment arm.
Two children are sitting on the see-saw, such that they can not swing. What is the net torque in this situation?
Ans: In this case, net torque such that they can swing. In this case, net torque would be zero because clockwise torque is equal to Anticlockwise torque.
A ladder leaning at a wall as shown in figure 4.31 is in equilibrium. How?
Ans: Ladder is in equilibrium because it satisfies second condition of equilibrium.
The weight of the ladder in figure 4.31 produces an anticlockwise torque. The wall pushes the ladder at its top end thus produces a clockwise torque. Does the ladder satisfy second condition for equilibrium?
Ans: Yes, it satisfies second condition of equilibrium because both torques are equal in magnitude but opposite in direction.
Does the speed of a ceiling fan go on increasing all the time?
Ans: Speed of ceiling fan does not increase all the times. At acquiring maximum speed it moves with uniform speed.
Does the fan satisfy second condition for equilibrium when rotation with uniform speed?
Ans: No, it does not satisfy the second condition of equilibrium. Because it neither in the state of rest nor moving with uniform velocity.
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