Recent content by davedays

it must be zero cause he's not going up, right ?

Ill try do a then : if the GF is pushing him down and NF is pushing him up then his weight is 70N cause the gravity force is greater by 70 N Second one: If the lift is going down then the gravity force must he smaller by 10 : 70-10 = 60 N Third one : vice versa 70+10=80 N Am I thinking...

so backward force is just 800 ?

So I think it would be gravity acting down and also the normal force pushing him up, correct ? Knowing that in the first case I subtract and in the second case I add the forces right ? However I still do not get the connecting between 'g' and the question. :(

I think the mistake is somewhere in the resultant force and then there is a follow through :(

I don't understand you, sorry. Can you explain again please ? Is F=ma all I need here ? I am not sure, however I really want to solve it :)

No mate I just checked twice with the textbook that's exactly ow the question looks like.

Can someone please help me ?

Can someone please help me ?

Homework Statement A man of mass 70 kg stands in a lift on a set of weighing scales. The scales are calibrated in Newtons. Assuming that g=10N kg -1 What weight will the scales register when the : a) lift is static b)lift accelerates down at 10 ms-2 c)lift accelerates up at 10 ms-2...

Homework Statement A car of mass 500kg climbs a 15 deg. hill. If the car's engine provides a forward thrust of 8000 N and the drag and friction on the car add up to 800 N calculate the car's rate of acceleration Homework Equations F=ma Normal F= mg x 15 deg The Attempt at a...

Homework Statement A man is standing on a frozen pond (which is mean less). He throws a ball m=250 g The speed of the ball is 8.0 ms-1 The man moves back at a speed of 0.05 ms-1 How heavy is the man ? Homework Equations p1=p2 m1 x v1 = m2 x v2 The Attempt at a Solution p1=p2...

thanks a lot guys

hmm not sure about that .. maybe I have another mistake m1 x v1 = m2 x v2 9 x 800 = 1800 x v2 7200 = 1800 v2 v2 = 7200 / 1800 v2 = 4 isnt it 4 ms -1 ?

Homework Statement A bullet m= 9.0 g leaves the barrel of a rifle with a speed = 8.0 x 10 ^2 ms-1 (by the may I am sure - is this 80 ms-1 ?) The mass of the rifle = 1.8 kg The rifle is free to move back Calculate the speed of recoilHomework Equations I figured I would need these : p=mv F=mv/t...