2002 - JAMB Physics Past Questions and Answers - page 1

Wt. in air = 0.25 N

Wt.in water = 0.15 N

therefore lost in wt. in water = Upthrust in water

                             = 0.25 - 0.15<br />

                             = 0.10 N.<br />

Wt. in paraffin oil = 0.17 N.

.. loss in wt.in oil = upthrust in the oil

Ratio upthrust in oil to upthrust in water

= 0.18/0.10 = 8/10 = 4/5 Or 4 : 5

Efficiency = M.A/V.R X 100/1 M.A = Load/Effort = 500/250

                                            = 2<br />

V.R. = radius of wheel/radius of axle = 0.4/0.1 = 4.

therefore Efficiency = 2/4 x 100/1 = 50 %

[ Density of blood = 1.1 x 10³ kgm^-3, g = 10ms^-2]

Pressure = pgh, where p = density, h = the height, g = acceleration of free fall due to gravity

1.6.5 x 10⁴ = 1.1 x 10³ x 10 x h

therefore h = 1.65 x 10⁴/1.1 x 10³ x 10 = 1.5m

Let M = mass of elevator

m = mass of the body

g = acceleration of free fall

a = upward acceleration of the elevator (5m/s^s)

when the elevator is at rest, the force it exerts on the body is equal to the weight of the body. And from Newtons third law, Mg = mg

However as the elevator ascends the net upward force F = Mg - mg = (M + m)a.

Thus, if the weight of the body = 80 N, then 88 its mass, m = 80/10 = 8kg.

Therefore M x 10 - 8 x 10 = (M + 8) 5

10M - 80 = 5M + 40

10M - 5M = 40 x 80

5M = 120 => M = 120/5 = 24kg.

Thus, net upward force = force exerted by the elevator floor on the body = (M x m)a

              = (24 x 8) x5<br />

              = 32 x 5<br />

              = 160 N

Let the distance apart the two masses = m.

From the equation F & M₁ m₂/ϒ²

F₁ α 10 x 10/ϒ² = F α 100/ ϒ²

F² α 10 X 10/(3ϒ)² => F² α 100/9ϒ²

therefore F²/F¹ = 100/9ϒ²/100/ϒ² = 100/9ϒ² ϒ²/100 = 1/9

Therefore F ₂ : F ₁ = 1 : 9

From Pythagoras,

R2 = 10^{2 + 102}

= 100 + 100

= 200

therefore R2 = √200 = √2 x 100

         = 10√2, in the direction 45°E

Angular velocity w = 2π f.

But f = frequency no. of oscillations per second.

 = 30/6 = 5Hz.<br />

therefore W = 2π x 5

        = 10π rad. s<sup>-1</sup>

Real depth = thickness of the glass block = 9cm.

Refractive index of the glass material = 1.5

But Refractive index = Real depth/Apparent depth

=> 1.5 = 9/Apparent depth

therefore Apparent depth = 9/1.5 = 6cm.

therefore Apparent displacement of the Coin = 9.6

                                        = 3cm

The function of the radiator of a motor car is to "collect" heat from the circulating water and radiate some out, but it is itself cooled by the fan adjacent to it. whose function is primarily based on convection