Laws of Motion

The net force acting is not zero on

• a retarding train

• a ball falling with terminal velocity

• a kite held stationary

• a truck moving with constant velocity

An engine of power 58.8 kW pulls a train of mass 2x10⁵ kg with a velocity of 36 kmh^-1. The coefficient of friction is

• 0.3

• 0.03

• 0.003

• 0.0003

If n bullets each of mass m are fired with a velocity v per second from a machine gun, the force required to hold the gun in position is

• (n + 1) mv

• $\frac{\mathrm{mv}}{{\mathrm{n}}^2}$

• mnv

• n²mv

A car moves at a speed of 20ms^-1 on a banked track and describes an arc of a circle of radius $40\sqrt{3}$. The angle of banking is (take g = 10 ms^-2)

• 25°

• 60°

• 45°

• 30°

A ball of mass 10 g moving perpendicular to the plane of the wall strikes it and rebounds in the same line with the same velocity. If the impulse experienced by the wall is 0.54 Ns, the velocity of the ball is

• 27 ms^-1

• 3.7 ms^-1

• 54 ms^-1

• 37 ms^-1

A cyclist bends while taking turn in order to

• reduce friction

• provide required centripetal force

• reduce apparent weight

• reduce speed

Two blocks of masses 2 kg and 4 kg are attached by an inextensible light string as shown in the figure. If a force of 120 N pulls the blocks vertically upward, the tension in the string is (take g = 10 ms^-2)

• 20 N

• 15 N

• 35 N

• 40 N

The total energy of a solid sphere of mass 300 g which rolls without slipping with a constant velocity of 5 ms^-1 along a straight line is

• 5.25 J

• 3.25 J

• 0.25 J

• 1.25 J

A constant force F acts on a particle of mass 1 kg moving with a velocity v, for one second. The distance moved in that time is

• 0

• $\frac{\mathrm{F}}{2}$

• $\mathrm{v} + \frac{\mathrm{F}}{2}$

• 2F

A spacecraft of mass 100 kg breaks into two when its velocity is 10⁴ ms^-1. After the break, a mass of 10 kg of the spacecraft is left stationary. The velocity of the remaining part is

• 10³ ms^-1

• 11.11 × 10³ ms^-1

• 11.11 × 10² ms^-1

• 10⁴ ms^-1