Motion in Straight Line

A coin is dropped in a lift. It takes time t₁ to reach the floor when the lift is stationary. It takes times t₂ when the lift is moving up with constant acceleration. Then:

• t₁ > t₂

• t₂ > t₁

• t₁ = t₂

• t₁ >> t₂

A police jeep is chasing with a velocity of 45 km/h, a thief in another jeep moving with velocity 153 km/h. Police fire a bullet with muzzle velocity of 180 m/s. The velocity with which it will strike the car of the thief is :

• 150 m/s

• 27 m/s

• 450 m/s

• 250 m/s

A car covers 2/5 of a certain distance with speed v₁ and rest 3/5 part with velocity v_2. The average speed of the car is :

• $\frac{1}{2}\sqrt{{\mathrm{v}}_1{\mathrm{v}}_2}$

• $\frac{5{\mathrm{v}}_1{\mathrm{v}}_2}{3{\mathrm{v}}_1+2{\mathrm{v}}_2}$

• $\frac{2{\mathrm{v}}_1{\mathrm{v}}_2}{{\mathrm{v}}_1+{\mathrm{v}}_2}$

• $\frac{{\mathrm{v}}_1+{\mathrm{v}}_2}{2}$

Apparent frequency of sound of engine is changing in the ratio 5/3 under the condition that engine is first aprroaching and then receding away from the observer. If velocity of sound is 340 m/s, then velocity of engine is

• 340 m/s

• 170 m/s

• 85 m/s

• 310 m/s

If a body travels half the distance with velocity v₁ and the next half with velocity v₂,its average velocity will be given by

• $\mathrm{v} = \sqrt{{\mathrm{v}}_1{\mathrm{v}}_2}$

• $\mathrm{v} = \frac{{\mathrm{v}}_1 + {\mathrm{v}}_1}{2}$

• $\mathrm{v} = \frac{{\mathrm{v}}_1}{{\mathrm{v}}_2}$

• $\frac{2}{\mathrm{v}} = \frac{1}{{\mathrm{v}}_1} + \frac{1}{{\mathrm{v}}_2}$

The ratio of the numerical value of the average velocity and average speed of body is always

• unity

• unity or less

• unity or more

• less than unity

A wheel of car is revolving at the rate of 1200 cycle/min. On pressing the accelerator, after 10s, it does 4500 cycle/min then radial acceleration of the wheel is

• 30 rad/s²

• 1880 degree/s²

• 40 rad/s²

• 1980 degree/s²

If a body loses half of its velocity on penetrating 3 cm in a wooden block then how much will it penetrate more before coming to rest?

• 1 cm

• 2 cm

• 3 cm

• 4 cm

A stone is dropped in 19.6 m depth well, echo is heard in  2.06 s, then velocity of sound is

• 315.2 m/s

• 320.5 m/s

• 326.7 m/s

• 332.4 m/s

An observer is coming towards plane mirror with a speed of 6 m/s, then apparent velocity of his image is

• 6 m/s

• 4 m/s

• 12 m/s

• 3 m/s