Short Answer TypeName a machine which can be used to,
i) multiply forces
ii) change the direction of the force applied
i) Inclined plane is used to multiply forces
ii) Pulley is used to change the direction of the force applied.
A ball of mass 200 g falls from a height of 5m. What will be its kinetic energy when it just reaches the ground?
K.E at the lowest point = P.E at the highest point
P.E at the highest point = mgh 
K.E when it just reaches the ground = 9.8 J
A coolie carrying a load on his head and moving on a frictionless horizontal platform does no work. Explain the reason why?
There is no work because the angle between the force applied (vertically upwards) and displacement of the load (along the horizontal) is 90o.
Using the formula,
W = Fd cos θ
W = Fd cos 90o = 0
Fill In the BlanksFill in the blanks in the following sentences with appropriate words:
During the emission of a beta particle, the ____ number remains the same.
Mass
Fill in the blanks in the following sentences with appropriate words:
The minimum amount of energy required to emit an electron from a metal surface is called ____.
Work function/ threshold energy
Short Answer TypeA man can open a nut by applying a force of 150 N by using a lever handle of length 0.4 m. What should be the length of the handle if he is able to open it by applying a force of 60 N.
Equating the torque in both the cases:
E1l1 = E2l2
150 × 0.4 = l2 × 60
Draw a diagram to show the energy changes in an oscillating simple pendulum. Indicate in your diagram how the total mechanical energy in it remains constant during the oscillation?
The energy changes in a simple pendulum is shown in the diagram below:
Where does the position of centre of gravity for,
i) a circle lamina
ii) a triangular lamina?
i) Centre of the circle or the point of intersection of diameters.
ii) Centroid or the point of intersection of its medians.
A uniform metre scale can be balanced at the 70.0 cm mark when a mass of 0.05 kg is hung from the 94.0 cm mark.
i) Draw a diagram of the arrangement.
ii) Find the mass of the metre scale.
i) The arrangement is as shown in the picture.
ii)
Let W be the wt. of the scale,
By principal of moments,
W x (70 – 50) = 0.05 (94 -70)
20 W = 0.05 x 24 
Define one Newton.
ii) Write the relation between S.I. unit and C.G.S. unit of force.i) One Newton is the amount of force required to produce an acceleration of 1 m/s2 in a body of mass 1 kg.
ii) 1 N =1 kg x 1 m/s2
= 103 x 102 gm cm/s2
1 N = 105 dynes
