JAMB Physics Past Questions & Answers - Page 459

2,291.

A rope is being used to pull a mass of 10kg vertically upward. Determine the tension in the rope if, starting from rest, the mass acquires a velocity of 4ms\(^{-1}\) in 8s [g = 10ms\(^{-2}\)]

A.

5N

B.

50N

C.

95N

D.

105N

Correct answer is D

Tension = Force of gravity + acceleration force

= mg + ma

\(a = \frac{v - u}{t}\)

= \(\frac{4 - 0}{8}\)

= 0.5 ms\(^{-2}\)

Tension = \(10 \times 10 + 10 \times 0.5\)

= 100 + 5

= 105N

2,292.

A stream is flowing at 0.75ms\(^{-1}\) and a boat heading perpendicular for the stream landed at the opposite bank at an angle of 30°. Calculate the velocity of the boat.

A.

1.50ms-1

B.

1.00ms-1

C.

0.86ms-1

D.

0.65ms-1

Correct answer is C

Let the velocity of the boat = Vm/s
0.75/V = adj/hyp = Cos 30°
0.75/V = 0.8660
∴ V = 0.75/0.8660
V = 0.866 ms\(^{-1}\)

2,293.

A catapult used to hold a stone of mass 500g is extended by 20cm with an applied force F. If the stone leaves with a velocity of 40m/s, the value of F is

A.

4.0 x 102N

B.

2.0 x 103N

C.

4.0 x 103N

D.

4.0 x 104N

Correct answer is C

Work done = kinetic energy of the stone 

\(\frac{1}{2} F e = \frac{1}{2} mv^2\)

Given m = 500g = 0.5kg; v = 40m/s ; e = 20cm = 0.2m

\(F = \frac{mv^2}{e}\)

= \(\frac{0.5 \times (40)^2}{0.2}\)

= 4.0 \(\times\) 10\(^3\) N

2,294.

If the force and the velocity on a system are each reduced simultaneously by half, the power of the system is

A.

doubled

B.

reduced to a quarter

C.

reduced by half

D.

constant

Correct answer is B

The Relation between PowerForce and Velocity is given by the relation:

P = F.V , this power is the product of force and velocity.

2,295.

At a fixed point below a liquid surface, the pressure downwards is P1 and pressure upwards is P2. It can be deduced that?

A.

P1 > P2

B.

P1 ≥ P2

C.

P1 < P2

D.

P1 = P2

Correct answer is D

As the temperature increases, the molecules in the gas move faster, impacting the gas's container more frequently and exerting a greater force. This increases the pressure. And similarly As the pressure goes up, the temperature also goes up. So the temperature and the pressure is directly proportional to each other. At a fixed point, temperature is kept constant. Hence, at this point, it can be deduced that \(P_{1} = P_{2}\)