# Physics question, need help A.S.A.P.

1. Nov 21, 2004

### Rapta3

Physics question, need help A.S.A.P.!!

What force is needed to accelerate a child on a sled (total mass = 61.0 kg) at 1.12 m/s2?

2. Nov 21, 2004

### Rapta3

I got another one,

If the coefficient of kinetic friction between a 37 kg crate and the floor is 0.25, what horizontal force is required to move the crate at a steady speed across the floor?

What horizontal force is required if µk is zero?

3. Nov 21, 2004

### Lorax

FORCE = MASS x Acceleration.

4. Nov 21, 2004

### stunner5000pt

to move it at a steady speed what is the sum of the forces? Another way of putting this question is what is the acceleration on the sled is the speed is CONSTANT

Once you figure that out what is the sum of the forces (applied and friction)?

5. Nov 21, 2004

### Rapta3

I need answers guys, i appreciate you trying to help me figure it out but I have no time, I have other things to do so plz help me if you can, I would greatly appreciate it, thanks.

6. Nov 21, 2004

### Rapta3

Is 73.2 N the correct answer for my first question?

7. Nov 21, 2004

### Rapta3

Help!!! Cmon!!

8. Nov 22, 2004

### vsage

Yes you're right on the first one. For the second one, the force required is = $$\mu_s m g$$

9. Nov 22, 2004

### Rapta3

Ok help me out then here, i know F=MA but for the first question i posted, i did that and the answer got was wrong so I dont know how to get the right answer...

10. Nov 22, 2004

### vsage

Friction force neglected, the force F can accelerate a child/sled of mass M to an acceleration A. I don't see how you could be wrong unless there's something in the question you didn't mention

11. Nov 22, 2004

### Rapta3

No thats the complete question....

12. Nov 22, 2004

### vsage

I didn't do the calculation but it looked right. You're off by 5N. 1.12*61 != 73.2

13. Nov 22, 2004

### Rapta3

thats what i said, look above i got 73.2

Last edited: Nov 22, 2004
14. Nov 22, 2004

### vsage

I help with math and physics, not arithmetic, sorry :(

15. Nov 22, 2004

### Rapta3

Ok someone help me with my second question, plz

16. Nov 22, 2004

### vsage

To move an object at a steady speed across a surface with friction you must apply a force equal to the friction. The same applies for the second part except there is no friction therefore you don't need any force.

17. Nov 22, 2004

### Rapta3

Ok thank you.

18. Nov 22, 2004

### Rapta3

If the coefficient of kinetic friction between a 39 kg crate and the floor is 0.25, what horizontal force is required to move the crate at a steady speed across the floor?

If it is what you say it is, it should be .25, but its not so what else is missing?

19. Nov 22, 2004

### vsage

The force of friction is equal to $$\mu_k mg$$ not just the coefficient of friction. Hope this helps.

20. Nov 22, 2004

### Rapta3

Ok well thanks for everything... time for some sleep, ill talk to guys later, bye.