_____________ forces are always attractive and the mass of an object determines how strong the ___________

Please, see the figure for a description of the problem. In red are the x and y-components of the gravity force (Fg). Since the y-component of Fg (Fgy) is of equal magnitude as Fn but in the opposite direction, both forces get canceled.

Then, the forces that cause the acceleration of the sled are the force of the wind (Fw), the friction force (Ff) and the x-component of the gravity force (Fgx).

The sum of all these forces make the sled move. Finding the resulting force will allow us to find the acceleration of the sled and, with it, we can find the time the sled travel.

The magnitude of the friction force is calculated as follows:

Ff = μ · Fn

where :

μ = coefficient of kinetic friction

Fn = normal force

The normal force has the same magnitude as the y-component of the gravity force:

Fgy = Fg · cos 30º = m · g · cos 30º

Where

m = mass

g = acceleration due to gravity

Then:

Fgy = m · g · cos 30º = 87.7 kg · 9.8 m/s² · cos 30º

Fgy = 744 N

Then, the magnitude of Fn is also 744 N and the friction force will be:

Ff = μ · Fn = 0.151 · 744 N = 112 N

The x-component of Fg, Fgx, is calculated as follows:

Fgx = Fg · sin 30º = m·g · sin 30º = 87.7 kg · 9.8 m/s² · sin 30º = 430 N

The resulting force, Fr, will be the sum of all these forces:

Fw + Fgx - Ff = Fr

(Notice that forces are vectors and the direction of the friction force is opposite to the other forces, then, it has to be of opposite sign).

Fr = 161 N + 430 N - 112 N = 479 N

With this resulting force, we can calculate the acceleration of the sled:

F = m·a

where:

F = force

m = mass of the object

a = acceleration

Then:

F/m = a

a = 479N/87.7 kg = 5.46 m/s²

The equation for the position of an accelerated object moving in a straight line is as follows:

x = x0 + v0 · t + 1/2 · a · t²

where:

x = position at time t

x0 = initial position

v0 = initial velocity

t = time

a = acceleration

Since the sled starts from rest and the origin of the reference system is located where the sled starts sliding, x0 and v0 = 0.

x = 1/2· a ·t²

Let´s find the time at which the position of the sled is 271 m:

271 m = 1/2 · 5.46 m/s² · t²

2 · 271 m / 5.46 m/s² = t²

The sled required almost 10 s to travel down the slope.

8 0

3 years ago

Why is it difficult to walk on muddy road?

Gnesinka [82]

Because of internal friction between layers of mud particles called viscosity. When you walk, your foot exerts a force on the mud; and according to Newton, the mud also (is supposed to) exert an equal opposite force, which leading to an equal net resultant force in your direction, propelling you forward.

3 0

3 years ago

Q1: A cyclist brakes to a stop. His thinking distance was 1m and his braking distance was 3m. What was his overall stopping dist

weeeeeb [17]

Answer:

1.) 4m

2.) 37 m

3.) 62m

4.) 2.5 s

Explanation:

1.) Given that the

Thinking distance = 1m

Breaking distance = 3m

Stopping distance = breaking distance + thinking distance

Stopping distance = 1 + 3 = 4m

2.) Given that the

Stopping distance = 52 m

Thinking distance = 15m

Breaking distance = 52 - 15 = 37m

3.) The stopping distance = 76m

Thinking distance = 14m

Breaking distance = 76 - 14 = 62m

It take the brakes 62m to slow the car down to a stop.

4.) Given that a lorry travels 28m when stopping from a speed of 4m/s. If its braking distance was 18m, what was the driver’s reaction time?

Thinking = stopping distance - braking distance

Thinking distance = 28 - 18 = 10m

Speed = distance/time

4 = 10/reaction time

Reaction time = 10/4

Reaction time = 2.5 s

5.) Question incomplete

5 0

3 years ago

_____________ forces are always attractive and the mass of an object determines how strong the ____________ pull is.

_ forces are always attractive and the mass of an object determines how strong the pull is.