Student’s Name:____________________________________ Student Number __ __ __ __ __ - __ __ __ __

Written Problems Answer on this sheet, clearly showing method and reasoning. Use diagrams as necessary. Write your final answers in the spaces provided in ink. [50 points total]

1. The mechanical “Canadarm” of the space shuttle can handle a 2200-kg load when extended to 12 m. Yet on the ground it cannot support its own weight. In the weightlessness of an orbiting shuttle why would the Canadarm have to be able to exert any force at all? [5]

In order to displace an object in orbit it must be accelerated and then deaccelerated again. (We’re talking about displacement with respect to the space shuttle.) Even though the object in orbit appears weightless, its mass remains what it is on earth. In order to accelerate an object with mass, force must be applied to it by the Canadarm (by Newton’s 2nd law) and that object will then apply a forceback on the Canadarm by Newton’s 3rd law.

2. In a tug-of-war three men pull on a rope to the left at one end and three men pull to the right at the other end. Then a 5-kg mass is hung from the centre of the rope. [5]

a) Can the men get the rope to be horizontal from end-to-end? _______NO____________b) If not, explain. If so, determine the magnitudes of the forces at both ends required to do this.

.An object hanging from the rope will apply a force downward. In order for the tension in the rope to bal-ance that force, the must be a vertical component to the rope’s orientation.

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2005 November 4Physics 140

3. A fan cart accelerates forward starting from rest. It covers 1.0 m in 1.0 s. A 0.50 kg mass in placed in the cart and then it again accelerates from rest. This time it takes 1.5 s to go 1 m. Assume the accelerations are constant and that the fan always exerts the same force. (Neglect friction.) [10]

a) What is the mass of the fan cart without the 0.50 kg mass? answer:__________________________________

b) What is the magnitude of the force exerted by the fan? answer:__________________________________

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2005 November 4Physics 140

6. A rock is thrown from the surface of the moon with initial velocity

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r v 1= (3.0 m/s)î + (4.0 m/s)ĵ, Where î is horizontal

and is ĵ vertical. The surface is level and there’s no air resistance. The local gravitational field strength on the moon is 1.7 N/kg. [10]

a) Write the velocity of the rock when it lands,

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r v 2 , using unit vector notation. _ (3.0 m/s)î + (–4.0 m/s)ĵ_

Find

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Δr v , the rock’s change in velocity during the flight.

b) answer: (3.0 m/s)î + (–4.0 m/s)ĵ – (3.0 m/s)î + (4.0 m/s)ĵ_= (–8.0 m/s)ĵ

c) Find the time of the rock’s flight, Δt

d) answer:_ Δt = |

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Δr v |/gmoon = (8m/s)/(1.7N/kg)_

e) Draw

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r v 1,

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r v 2 , and

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Δr v . Label the vectors and indicate the scale.

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2005 November 4Physics 140

€

Δr v

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r v 1

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r v 2

1 division = 1 m/s

7. A 0.20 kg bouncy ball going in the +x direction hits the wall with a speed of 5.0 m/s and rebounds back with a speed of 3.0 m/s. [5]

a) What is the ball’s change in momentum? (magnitude and direction) answer:_Δp=(0.2 kg)(–3m/s–5m/s)= –1.6 kg m/s in the –x direction

b) If the contact time of the ball with the wall is 0.1 s, what is the average force on the wall during the colli-sion? (magnitude and direction) answer: Favg = Δp/Δt = 16 N in the +x direction

c) What is the average force on the ball during the collision? (Assume the wall is much more massive than the ball. Give magnitude and direction) answer: 16 N in the – x direction by Newton’s 3rd law..

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2005 November 4Physics 140