A person pushes a block of mass 0.25kg along a horizontal table with a force of magnitude 5N for a distance of 0.5m. The friction force between block and table is 1N. The average power of pushing force is?
(1) 20W
(2) 10W
(3) 40W
(4) 0.5W
Answers
Given data : -
- A person pushes a block of mass 0.25kg along a horizontal table with a force of magnitude 5N for a distance of 0.5m.
- The friction force between block and table is 1N.
Solution :-
Here, {according to given}
→ mass of block, m = 0.25 kg
→ force acting on block, F = 5 N
→ distance covered by block, {displacement} s = 0.5 m
→ frictional force between block and table, F' = 1 N
Now, work done ( W ) by force acting on block, W = F × s hence,
→ W = F × s
→ W = 5 × 0.5
→ W = 2.5 Joule ......( 1 )
Block moves forward when it opposes frictional forces, hence resultant force :
→ Resultant force = F - F'
→ Resultant force = 5 - 1
→ Resultant force = 4 N ......( 2 )
Now, we use formula of force {Here we use resultant force because block moves in forward direction}
→ force = mass × acceleration i.e.
→ Resultant force = mass × acceleration
{from given}
→ 4 = 0.25 × acceleration i.e.
→ acceleration = 4/0.25
→ acceleration = 16 m/s² {a = 16 m/s²}
Let, initial velocity, u be zero,
Now we use kinematical equation to find time taken by partical to cover distance 0.5 m.
→ s = ut + ½ at²
→ 0.5 = 0 × t + ½ × 16 × t²
→ 0.5 = 8 × t² i.e.
→ t² = 0.5/8
→ t² = 0.0625
→ t = √0.0625
→ t = 0.25 sec ......( 3 )
Now, to find average power of pushing force we use fomula of power
→ Power = work/time
{from ( 1 ) & ( 3 )}
→ Power = 2.5/0.25
→ Power = 10 watt {10 joule/sec}
Hence, the average power of pushing force is 10 watt.
{Answer : ( 2 ) 10 watt }
Learn more :
- A ball is thrown upwards with the velocity of 29.4 m/sec in the absemce of air resistence .find the time taken by the ba...
https://brainly.in/question/4646603
- A car travelling at 90 m/s comes to rest in 10 sec , calculate its distance travelled after brakes were applied.
https://brainly.in/question/26454557