A boat has a mass of 6796 kg. Its engines generate a drive force of 4062 N, due

Question

A boat has a mass of 6796 kg. Its engines generate a drive force of 4062 N, due west, while the wind exerts a force of 839 N, due east, and the water exerts a resistive force of 1202 N due east. What is the magnitude of the boat's acceleration?

A 1560 kg car is traveling with a speed of 13.3 m/s. What is the magnitude of the horizontal net force that is required to bring the car to a halt in a distance of 45.9 m?

A 35.9 kg crate rests on a horizontal floor, and a 82.7 kg person is standing on the crate. Determine the magnitude of the normal force that the floor exerts on the crate.

A supertanker (mass = 1.78E+8 kg) is moving with a constant velocity. Its engines generate a forward thrust of 7.29E+5 N. Determine the magnitude of the resistive force exerted on the tanker by the water.

Explanation / Answer

The resistive forces wants to stop your boat from going forward, therefore you subtract those from the force pushing you forward:
4063 - 739 - 1202 = 2122N

Use: F = m x a <----> a = F/m
-----> a = 2122/6796 = 0.312 ms^(-2)

we find force from F = m a

we find the acceleration from:

vf^2=v0^2+2ad where vf=final speed =0
v0=initial speed = 13.3 m/s
d=distance=50m

therefore, we have

0=13.3^2+2a(45.9) or
a = -13.3^2/2(45.9) = 1.92 m/s/s

the minus sign indicates slowing down

then the force required to stop the car is

F = 1560 kg x (-1.92 m/s/s) = 2995.2N

. f = ma = (35.9+82.7)*9.8 =1162.28 N

You can actually start with F = MA

If there is constant velocity, then there is no acceleration. We know the mass times acceleration equals the sum of the forces in the direction of movement, but is the acceleration is zero, then the sum of the forces equals zero, so the force pushing the boat forward must be the same as the force holding it back.

Resistive force = 7.29x 10^5 Newtons

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