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Tuesday, October 16, 2018

Which statement includes a correct unit? A energy = 7.8 N s


Question 7
Which statement includes a correct unit?
A energy = 7.8 N s
B force = 3.8 N s
C momentum = 6.2 N s
D torque = 4.7 N s





Reference: Past Exam Paper – June 2015 Paper 13 Q1





Solution:
Answer: C.

The unit Ns indicates the product of the quantity having unit N and quantity having unit s. That is, force × time.


Energy is force × distance. [A is incorrect]


The unit of force is N, so N s is an incorrect unit for force. [B is incorrect]


Force = Δp / t
Δp = F × t
So, momentum can have unit N × s. [C is correct]


Torque = Force × distance
So, unit of torque: N m, not N s. [D is incorrect]

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