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# A block of mass 6kg is placed on a horizontal floor. when it is pulled by a force of 30N, it moves with a constant speed of 15 m/s.?

(a) calculate the resultant force?

(b) calculate the frictional force?

(c) the block is now pulled with a force of 35N for 3s calculate

(i) the acceleration?

(ii) the speed of the block after 3s?

please help!

### 1 Answer

- sojsailLv 77 years agoFavorite Answer
Ooops, I didn't see question c till submiting a and b. Pretend this is at the bottom.

c. Fres was 0 when applied force was 30. So now Fres=5N.

i. Fres = mass*acceleration

Solve for accel.

ii. Use the kinematic formula

Vf = Vi + a*t

where Vi is initial velocity = 0, a is accel, and t is 3 s.

_________________________________

I started here.

Constant speed, so acceleration is zero.

Fres = mass * acceleration

That is Newton's 2nd law

Fres = 6 kg * 0 = 0

Fres is the resultant of forces on the block.

Fres = applied force + friction

You know from above that Fres is zero and applied force is given as 30N. Plug 'em in and solve for friction.