# Physics HELP!

A block of mass 3 kg slides along a horizontal surface while a 20-N force is applied to it at an angle of 25°. If needed, use g = 10 m/s2. For a coefficient of kinetic friction of 0.3 between the block and the surface, the frictional force acting on the block is most nearly

9 N
8.5 N
15 N
6 N
12 N

1. 👍
2. 👎
3. 👁
1. friction=mu*mg=.3*3*10 N

1. 👍
2. 👎
👤
bobpursley
2. Is the 25 degree angle of the applied force above or below horizontal? It makes a big difference in the answer.

1. 👍
2. 👎
3. If the angle is 25 degree below the horizontal, then the upward component makes the friction lighter (less normal force).

friction=mu(normal force)
= .3(mg-20sin25)
=.3(30-8.45)

so assuming the 25 is above the horizontal, friction will be greater..
friction= = .3(mg+20sin25)
=.3(38.45)= almost 12 N

1. 👍
2. 👎
👤
bobpursley
4. F(y) = F•sinα =20•sin25º =8.45 N.
The force may be applied
\ from top downward
or / from the bottom upward ,
then
F(fr) =μ•N = μ•[mg ± F(y)] =
= 0.3•{3•10 ± 8.45) =
= 11.54 N or 6.5 N,

1. 👍
2. 👎

## Similar Questions

1. ### Physics

A block slides from rest with negligible friction down a track, descending 5.0m to point P at the bottom. It then slides on the horizontal surface. The coefficient of friction between the block and the horizontal surface is 0.20.

2. ### physics

The horizontal surface on which the block of mass 4 kg slides is frictionless. The force of 30N acts on the block in a horizontal direction and the force of 60N acts on the block at an angle. What is the magnitude of the resulting

3. ### physics

The horizontal surface on which the block of mass 5.1 kg slides is frictionless. The force of 62 N acts on the block in a horizontal direction and the force of 124 N acts on the block at an angle of 60 degrees. What is the

4. ### Physics

A horizontal force, F1 = 85 N, and a force, F2 = 18.4 N acting at an angle of θ to the horizontal, are applied to a block of mass m = 2.1 kg. The coefficient of kinetic friction between the block and the surface is μk = 0.2. The

1. ### physics

[20 pts] A 2.00 kg block is pushed against a spring with negligible mass and force constant k = 400 N/m, compressing it 0.220 m. When the block is released, it moves along a frictionless, horizontal surface and then up a

2. ### physics

The 2 kg block in Figure 7-25 slides down a frictionless curved ramp, starting from rest at a height of h = 3 m. The block then slides d = 12 m on a rough horizontal surface before coming to rest. Figure 7-25 (a) What is the speed

3. ### Physics

A metal block of mass 5kg lies on a rough horizontal platform. If a horizontal force of 8 N applied to the block through its center of mass just slides the block on the platform, then the coefficient of limiting friction between

4. ### physics

A small block with mass 0.308 kg is sliding down a frictionless ramp that is inclined at an angle of 53.1° above the horizontal. Assume g = 9.80 m/s2. (a) As the object slides down the incline, what is the magnitude of the normal

1. ### Physics

a 2.5kg block initially at rest on horizontal surface. A horizontal force F of magnitude 6N and a vertical force P are the applied to the block. The coefficients of friction for the block and surface are Ms=0.4 and

2. ### Impulse and Momentum

A bullet of mass m is fired at speed v0 into a wooden block of mass M. The bullet instantaneously comes to rest in the block. The block with the embedded bullet slides along a horizontal surface with a coefficient of kinetic

3. ### Physics

A block of mass 3m is placed on a frictionless horizontal surface, and a second block of mass m is placed on top of the first block. The surfaces of the blocks are rough. A constant force of magnitude F is applied to the first

4. ### Physics

1)How much work is done by a person lifting a 2 kg object from the bottom of a well at a constant speed of 2m/s for 5 s. Is the answer mgh=2*9.8*10m 2)A 2kg block slides on a rough horizontal surface. A force (magnitude = 4N)