Physics Dynamics

Jasmine ngjiamin SG

Block of wood 2kg was pushed along horizontal flat surface of bench, friction force measured was 4N. When this block is pushed along the same bench with a force of 10N, it moved with a aceleration of 3m/s2.

However, my answer is 5m/s2. This is my working:

F=Ma

10N=2kg(a)

a=5m/s2

please tell me where i have gone wrong, thank you.

CaiHongRainx SG

F = ma , F is the resultant force
10 - 4 = 2(a)

6 = 2a

a = 3m/s2.

I guess this is the way.

Toiletries SG

In explanation, while 10N was required to push a 2kg block and achieve an acceleration of 3 m/s^2, 4N was consumed to overcome frictional forces leaving you with 6N to do the work.

eagle SG

Hi,

we have to begin with the definition of Newton's 2nd Law.

I assume you are in O levels, so the definition would be the resultant force on an object is equal to the mass times the acceleration of the object.

Next, draw the free body diagram of the object. 10N is the forward force, while 4N is the resistive force. This leaves us with a resultant force of 10 - 4 = 6N.

Since F = ma, where F = 6 and m = 2, this leaves us with a = 3.

Hope this answers your questions :)