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A block weighing 200 N is in contact with a level plane whose coefficients of static and kinetic friction are 0.4 and 0.2, respectively. The block is acted upon by a horizontal force (in newton) P = 10t, where t denotes the time in seconds. The velocity (in m/s) of the block attained after 10 seconds is __________.
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- 4.9
- 4.6
- 4.5
- 4.4
Correct Option: A
∑Fv = O
N = mg = 200 N
(fs )max = μs N = 0.4 × 200 = 8 0 N
As given in the question, upto 8 sec [P=10 t]→ no motion
⇒ From 8 sec to 10 sec
fK = μKN = 0.2×200 = 40 N
Average applied force is given by,
| Pang = | = | = 90N | ||
| 2 | 2 |
Average Resultant force = Avg. app. force – kinetic friction
= 90 – 40 = 50 N
Average acceleration
| = | 200 |
⇒ V = u + at [∴ u = O]
| a = | 200 |
t = 2 second
| ∴ V = | × 2 = 4.9 m/s | 200 |
