Physics Pre AP



Physics PreAP

Force Problems

1) Once ignited, a small rocket motor on a spacecraft exerts a constant force of 10 N for 7.8 s. During the burn the rocket causes the 100 kg craft to accelerate uniformly. Determine the acceleration. (0.10 m/s2)

2) A force acts on a 2.0 kg mass and gives it an acceleration of 3.0 m/s2. What acceleration is produced by the same force when acting on a mass of (a) 1.0 kg? (b) 4.0 kg? (c) How large is the force? (6.0 m/s2; 1.5 m/s2; 6.0 N)

3) An object has a mass of 300 g. (a) What is its weight on Earth? (b) What is its mass on the Moon? (c) What will be its acceleration on the Moon when a 0.5 N resultant force acts on it? (2.9 N; 0.3 kg; 1.7 m/s2)

4) Typically, a bullet leaves a standard 45-caliber pistol at a speed of 262 m/s. If it takes 1 millisecond to traverse the barrel, determine the average acceleration experienced by the 16.2 gram bullet within the gun and then compute the average force exerted on it. (2.6 x 105 m/s2; 4.2 x 103 N)

5) A horizontal cable pulls a 200 kg cart along a horizontal track. The tension in the cable is 500 N. Starting from rest,

(a) How long will it take the cart to reach a speed of 8.0 m/s? (b) How far will it have gone? (3.2 s; 12.8m)

Free-body diagrams and ∑F statements are required from this point on!!!

6) A 5.0-kg mass hangs at the end of a cord. Find the tension in the cord if the acceleration of the mass is (a) 1.5 m/s2 up, (b) 1.5 m/s2 down, (c) 9.8 m/s2 down. (57 N; 42 N; 0 N)

7) A 20 kg crate hangs at the end of a long rope. Find its acceleration (magnitude and direction) when the tension in the rope is (a) 250 N, (b) 150 N, (c) zero, (d) 196 N (2.7m/s2 up; 2.3 m/s2 down; 9.8 m/s2)

8) A 700-N man stands on a scale on the floor of an elevator. A scale “reads” the Normal force that exists between it and the object on it. What is the scale reading if the elevator has an acceleration of (a) 1.8 m/s2 up? (b) 1.8 m/s2 down? (c) 9.8 m/s2 down? (828 N, 571 N, zero)

9) An elevator starts from rest with a constant upward acceleration. It moves 2.0 m in the first 0.60 s. A passenger in the elevator is holding a 3.0 kg package by a vertical string. What is the tension in the string during the accelerating process? (63 N)

Atwood’s Machine

10) An Atwood’s Machine consists of a cord passing over a frictionless, massless pulley as shown below. It has a 4.0-kg object tied to one end and a 12.0 kg object tied to the other. Calculate the acceleration of the system and the tension in the cord. (4.9m/s2, 59 N)

Forces involving angles

11) A 40 Kg crate is pulled across an icy surface with a rope. A force of 100 N is applied at an angle of 30 degrees with the horizontal to a rope attached to the crate, as shown above. Neglecting friction, calculate the acceleration of the crate. Calculate the upward force the ice exerts on the crate as it is pulled. (2.2 m/s2, 342 N up)

12) A 50 kg sign is hung by two cables as shown below. What is the tension in each of the cables? (381 N)

40o 40o

13) An Olympic skier coasts down a 5.0 m long slope with an angle of 370. Neglecting friction, what is the acceleration of the skier? If the skier has a speed of 5.0 m/s at the top of the slope, what is his speed when he reaches the bottom of the slope? (5.9 m/s2, 9.2 m/s)

14) A cord holds stationary a block (shown below) of mass 15 kg on a frictionless plane that is inclined at an angle of 270. a.) What is the tension in the cord, and the normal force on the block? (66.7 N, 131 N)

b.) The cord is cut and the block accelerates down the ramp. What is this acceleration? (4.4 m/s2)

15) In the apparatus shown below, m1 = 2.0 kg, and the angle is 25o. What is m2 if both masses are at rest? Ignore friction. (0.85 kg)

-----------------------

m2

m1

Box of Rocks

30o

King Toot’s Music Store

25o

2

1

Recommended reading Essential Physics by Hsu:

•

fg×Ûèéòóôõ? @ Á Å Æ É Ê Ó Ô Ú Ü Ÿ£¤ñâÐÀЮЮ›†›ÀâvâfVfDfDVfâfV"hÕh[2Ù6?CJH*[pic]OJQJaJhÕhÏ\%6?CJOJQJaJhÕh[2Ù6?CJOJQJaJhÕh¾CJH*[pic]OJQJaJ(hÕh[2Ù5?6?CJH*[pic]OJQJ\?aJ%hÕh[2Ù5?6?CJOJQJ\?aJ"hÕh[2Ù5?CJOJQJ\?aJhÕh¾5?Chapter Five: Forces/Newton’s Law’s of Motion/FBD’s

➢ Read p. 132-148

➢ Review Questions p.167 #124-126, 130-135

• Chapter Six: FBD’s & Angles

➢ p. 170-177, p.194

➢ Review Questions See Mr. D

Also Recommended:

• Newton’s Laws Lessons 1-4

• #physics

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