Laws of Motion
Topics
Chapter tests
See all →Top questions
See all →- A ball of mass 0.5 kg is dropped from a height of 40 m. The ball hits the ground and rises to a height of 10 m. The impulse imparted to the ball during its collision with the ground is (Take g = 9.8 m/s^2) Answer: 1. 21 NS Key idea: impulse equals change in momentum, and the velocity direction reverses at the ground. v_before=√(2gh₁)=√(2×9.8×40... 1
- There are two inclined surfaces of equal length (L) and same angle of inclination 45^° with the horizontal. One of them is rough and the other is perfectly smooth. A given body takes 2 times as much time to slide down on rough surface than on the smo… Answer: 4. 0.75 Key idea: for a fixed length L starting from rest, L=1/2 a t² , so t∝ 1/sqrt a . Smooth plane: a_s=gsin45^° . Rough plane: a... 1
- A bob is whirled in a horizontal plane by means of a string with an initial speed of ω rpm. The tension in the string is T. If speed becomes 2ω while keeping the same radius, the tension in the string becomes : Answer: 3. 4T Key idea: The tension supplies the centripetal force: T=mω²r . With the same m and r , T∝ω² . Doubling the speed (rpm) gives T... 1
- A horizontal force 10 N is applied to a block A as shown in figure. The mass of blocks A and B are 2 kg and 3 kg, respectively. The blocks slide over a frictionless surface. The force exerted by block A on block B is : Answer: 4. 6 N Key idea: Both blocks move together with the same acceleration. Find it first, then use it for block B. a=F/m_A+m_B=10/2+3=2... 1
- Calculate the maximum acceleration of a moving car so that a body lying on the floor of the car remains stationary. The coefficient of static friction between the body and the floor is 0.15 (g=10 m s^-2). Answer: 4. 1.5 mathrmm s⁻² The body stays at rest relative to the car only while the pseudo-force ma is balanced by static friction, whose m... 1
- A football player is moving southward and suddenly turns eastward with the same speed to avoid an opponent. The force that acts on the player while turning is : Answer: 4. along north-east Force is along the change in velocity, vec F∝ Δvec v=vec v_f-vec v_i . Initially the velocity is southward, -vha... 1