Motion — Set 2
Physics · गति · Questions 11–20 of 60
Inertia is the property of a body to?
Correct Answer: C. Change its motion easily
Inertia is the tendency to oppose changes in motion. A body at rest tends to remain at rest, and a moving body tends to continue uniformly. This concept is linked to Newton’s first law.
Two trains move in opposite directions with speeds 40 km/h and 60 km/h. What is their relative speed?
Correct Answer: D. 100 km/h
For opposite directions, relative speed is the sum of speeds. So relative speed = 40 + 60 = 100 km/h. Hence, 100 km/h is correct.
Which relation between angular speed (ω) and time period (T) is correct?
Correct Answer: D. ω = π/T^2
One full revolution is 2π radians completed in time T. So angular speed ω = angle/time = 2π/T. Therefore, ω = 2π/T is correct.
A ball is thrown upward with initial speed 20 m/s. Taking g = 10 m/s^2, what maximum height does it reach?
Correct Answer: C. 10 m
At the top, v = 0 and use v^2 = u^2 + 2as with a = -g. So 0 = 20^2 - 2×10×h, giving h = 400/20 = 20 m. Hence, 20 m is the maximum height.
Which is true about static friction?
Correct Answer: C. It acts only when there is relative motion
Static friction acts when surfaces tend to slip but do not actually slip. Its value adjusts up to a maximum limit. That maximum is μsN, so the statement about μsN is correct.
A projectile is launched with speed u at angle 30° to the horizontal. Which expression gives the horizontal component of its velocity?
Correct Answer: C. u cos 30°
The horizontal component of velocity is u cosθ. For θ = 30°, it becomes u cos 30°. The horizontal component remains constant if air resistance is ignored.
In uniform circular motion, the work done by the centripetal force on the body is?
Correct Answer: A. Zero
Centripetal force is always perpendicular to instantaneous displacement. A perpendicular force does no work because W = F·s = Fs cos 90°. So the work done by centripetal force is zero.
A body moves in a circle of radius 2 m with speed 6 m/s. What is its centripetal acceleration?
Correct Answer: B. 18 m/s^2
Centripetal acceleration a = v^2/r. Here v^2 = 36 and r = 2, so a = 36/2 = 18 m/s^2. Therefore, 18 m/s^2 is correct.
The area under a velocity–time graph between two times represents?
Correct Answer: D. Displacement
Area under v–t graph equals ∫v dt, which gives displacement. If velocity stays positive, it also equals distance traveled. Therefore, the area represents displacement.
A body increases its speed from 10 m/s to 30 m/s in 5 s. What is the acceleration?
Correct Answer: D. 5 m/s^2
Use a = (v - u)/t with v = 30, u = 10, t = 5. So a = (30 - 10)/5 = 4 m/s^2. Hence, 4 m/s^2 is correct.