Here are the solutions to the questions:
Question 1.1
- Concept: Newton's Second Law of Motion states that the net force acting on an object is equal to the rate of change of its momentum.
- Formula: F=ΔtΔp
- Explanation: This formula directly defines force as the rate of change of momentum.
The correct option is D.
DForce
Question 1.2
- Concept: For an object in free fall (ignoring air friction), the acceleration due to gravity (g) is constant. Momentum (p) is the product of mass (m) and velocity (v).
- Step 1: Determine velocity at time t.
Since the object is dropped, its initial velocity u=0.
Using the kinematic equation v=u+at, where a=g:
vt=0+gt=gt
- Step 2: Express momentum at time t.
p=mvt=mgt
- Step 3: Determine velocity at time 2t.
v2t=0+g(2t)=2gt
- Step 4: Express momentum at time 2t.
Let the momentum at time 2t be p′.
p′=mv2t=m(2gt)
p′=2(mgt)
- Step 5: Relate p′ to p.
Since p=mgt, we can substitute this into the expression for p′:
p′=2p
The correct option is C.
C2p
Question 1.3
- Concept: According to Newton's Third Law of Motion, for every action, there is an equal and opposite reaction. If the boy exerts a force on the box, the box exerts an equal and opposite force on the boy.
- Explanation: The boy pushes the box with a force of 250 N. Therefore, the box exerts a force of 250 N back on the boy. The frictional force of 50 N acts on the box, opposing its motion, but it is not part of the action-reaction pair between the boy and the box.
The correct option is C.
C250N
Question 1.4
- Concept: Positional isomers are compounds that have the same molecular formula and the same carbon skeleton, but differ in the position of a functional group, substituent, or multiple bond.
- Step 1: Determine the molecular formula and identify the carbon skeleton for each compound.
- I: CH≡C−CH2−CH3
- Molecular formula: C4H6
- Name: But-1-yne (4-carbon chain, triple bond at position 1)
- II: CH3−C≡C−CH2−CH3
- Molecular formula: C5H8
- Name: Pent-2-yne (5-carbon chain, triple bond at position 2)
- III: CH3−C≡C−CH3
- Molecular formula: C4H6
- Name: But-2-yne (4-carbon chain, triple bond at position 2)
- IV: CH3−C≡CH
- Molecular formula: C3H4
- Name: Propyne (3-carbon chain, triple bond at position 1)
- Step 2: Identify compounds with the same molecular formula and carbon skeleton but different positions of the multiple bond.
- Compounds I and III both have the molecular formula C4H6 and a 4-carbon chain (butyne).
- In compound I, the triple bond is between the first and second carbon atoms (But-1-yne).
- In compound III, the triple bond is between the second and third carbon atoms (But-2-yne).
- They differ only in the position of the triple bond.
Therefore, compounds I and III are positional isomers.
IandIII