1. A football player pushes a dummy forwards at a constant 0.85m/s for 11m using 7150 J of energy. The dummy has a mass of 120 kg. Find the force the football player exerts, find the frictional force the dummy exerts.

- for my answer I got 1176N as the force the football player exerts. I don't know how to find the frictional force the dummy exerts. Is the mass necessary to find the frictional force?

2. If given the horizontal and vertical force how would the actual force be found?

Would it be the net force?

7150 = F * 11

so
F = 650 Newtons exerted by player
since the velocity is constant that is exactly equal and opposite to the friction force

Just use horizontal force. There is no up or down motion so vertical force does no work.

4n

1. To find the force exerted by the football player, we can use the work-energy theorem. The work done by the player is equal to the change in kinetic energy of the dummy:

Work done = Change in kinetic energy

The change in kinetic energy can be calculated using the formula:

Change in kinetic energy = (1/2) * mass * (final velocity^2 - initial velocity^2)

Here, the initial velocity is 0 m/s since the dummy starts from rest. The final velocity is given as 0.85 m/s. The mass of the dummy is given as 120 kg.

So, the change in kinetic energy = (1/2) * 120 kg * (0.85 m/s)^2 = 51 J

Now, since the work done is 7150 J, we can write:

Work done = Force * Distance

7150 J = Force * 11 m

So, the force exerted by the football player is:

Force = 7150 J / 11 m = 650 N (approximately)

To find the frictional force exerted by the dummy, we can use Newton's second law of motion, which states that Force = mass * acceleration.

However, without any additional information about the acceleration of the dummy, it is not possible to calculate the frictional force accurately. The frictional force depends on factors such as the coefficient of friction, the normal force, and the nature of the surface.

To answer your questions:

1. To find the force the football player exerts, you can use the work-energy principle. The work done by the football player is equal to the energy used (work-energy principle: work = force × distance). Therefore, the force exerted by the football player can be calculated by dividing the energy used by the distance traveled (force = work / distance). Substituting the given values, force = 7150 J / 11 m = 650 N. So, it seems your answer of 1176 N is incorrect.

To find the frictional force the dummy exerts, we can consider that the net force acting on the dummy is zero because it moves at a constant speed. There are two forces acting on the dummy: the force exerted by the football player and the frictional force. Since the net force is zero, the force exerted by the football player and the frictional force must cancel each other out. Therefore, the frictional force the dummy exerts is equal in magnitude but opposite in direction to the force exerted by the football player, which in this case is 650 N.

2. If you are given horizontal and vertical forces, and you want to find the actual force, you can use vector addition. The actual force acting on an object can be found by adding the horizontal and vertical forces as vectors. You can use the Pythagorean theorem to find the magnitude of the resulting force, and the tangent of the angle to find its direction.