Momentum of an object is a product of its mass and velocity.
a) Classify momentum as a scalar or vector quantity.
b) What is the SI unit of momentum?
c) A girl of mass 30kg jumps with a horizontal velocity of 7ms-1onto a stationary cart with
frictionless wheels. The mass of the cart is 5kg. What is the velocity of the girl as the cart starts
moving? Assume that there is no external unbalanced force working in the horizontal direction
Answers
Explanation:
1) Momentum is vector quantity.
2) Kg.m/
Answer:
Momentum of an object is a product of its mass and velocity.
a) Classify momentum as a scalar or vector quantity.
Ans. Momentum is a vector quantity.
➩ The physical quantities which are expressed in magnitude as well as direction are called vector quantities. So, momentum is a vector quantity which can be expressed in both magnitude as well as direction.
b) What is the SI unit of momentum?
Ans. It's unit is newton second ( Ns )
Mathematically, 1 Ns = 1 kgms^-1
In CGS system, it's unit is dyne second.
Mathematically, 1 dyne second = 1gcms^-1
c) A girl of mass 30 kg jumps with a horizontal velocity of 7 ms^-1 onto a stationary cart with frictionless wheels. The mass of the cart is 5 kg. What is the velocity of the girl as the cart starts moving? Assume that there is no external unbalanced force working in the horizontal direction.
Ans.
Let the v be the velocity of the girl on the cart as the cart starts moving.
The total momenta of the girl and the cart before the interaction
= 30 kg × 7 m/s + 5 kg × 0 m/s
= 30 × 7 + 5 × 0
= 210 + 5
= 215 kg m/s
The total momenta of the girl and the cart after the interaction
= ( 30 + 5 ) kg × v m/s
= 35 v kg m/s
According to the law of conversion of momentum, the total momentum is conserved during the interaction.
⇛ 35 v kg m/s = 215 kg m/s
⇛ 35 v = 215
⇛ v = 215/35
⇛ v = 6.14 m/s
⇛ v = + 6.14 m/s
∴ The girl on the card would move with velocity of 6.14 m/s in the direction in which the girl jumped.
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