Question

A 65 kg bobsled is pushed along a horizontal surface by two athletes. After the bobsled is pushed a distance of 6.5 m starting from rest, its speed is 7.0 m/s. Find the magnitude of the net force on the bobsled.

Answer 1

Answer:

245 N

Explanation:

Force is given by mass × acceleration. The mass is given and we need to determine the acceleration.

The bobsled starts from rest; its initial velocity is 0.0 m/s. After a distance of 6.5 m, its speed is 7.0 m/s

We use the equation of motion:

$v^2 = v_0^2 + 2as$

$a = \dfrac{v^2-v_0^2}{2s}$

v is the final velocity, $v_0$ is the initial velocity, a is the acceleration and s is the distance.

$a = \dfrac{7.0^2-0.0^2}{2\times6.5} = \dfrac{49}{13}$

The net force is

$F = 65\times\dfrac{49}{13} = 245\text{ N}$

Answer 2

Answer:

245.05 N

Explanation:

From Newton's law of fundamental equation,

F = ma................. Equation 1

Where F = Force, m = mass of the bobsled, a = acceleration,

But

v² = u²+2as.................... Equation 2

Where v and u = final and initial velocity respectively, s = distance.

Given: v = 7 m/s, u = 0 m/s, s = 6.5 m

Substitute into equation 2

7² = 0²+2(6.5)(a)

49 = 13a

a = 49/13

a = 3.77 m/s²

Also Given: m = 65 kg,

Substitute into equation 1

F = 65(3.77)

F = 245.05 N