# 25 pt. 5 pt. 10 pt. 15 pt. 20 pt. 25 pt. 5 pt. 10 pt. 15 pt. 20 pt. 25 pt. 5 pt. 10 pt. 15 pt. 20 pt. 25 pt. 5 pt. 10 pt. 15 pt. 20 pt. 25.

## Presentation on theme: "25 pt. 5 pt. 10 pt. 15 pt. 20 pt. 25 pt. 5 pt. 10 pt. 15 pt. 20 pt. 25 pt. 5 pt. 10 pt. 15 pt. 20 pt. 25 pt. 5 pt. 10 pt. 15 pt. 20 pt. 25."— Presentation transcript:

25 pt. 5 pt. 10 pt. 15 pt. 20 pt. 25 pt. 5 pt. 10 pt. 15 pt. 20 pt. 25 pt. 5 pt. 10 pt. 15 pt. 20 pt. 25 pt. 5 pt. 10 pt. 15 pt. 20 pt. 25 pt. 5 pt. 10 pt. 15 pt. 20 pt.

1-5 A physics textbook is sitting on the table in front of you. Are there any forces acting on it? (Draw a FBD)

1-5A A physics textbook is sitting on the table in front of you. Are there any forces acting on it? (Draw a FBD) Yes, the book’s weight pulling down and the table pushing up. FNFN FgFg

1-10 Which string pulls harder on the hanging mass? 2 1

1-10A Which string pulls harder on the hanging mass? 2 1 String #1 F T1 FgFg F T2

1-15 Draw a free-body diagram of the forces acting on the object below. It is a stone sliding (with friction) down a ramp. Label all forces!

1-15A Draw a free-body diagram of the forces acting on the object below. It is a stone sliding (with friction) down a ramp. Label all forces! F g FfFf FNFN

1-20 If the ball on the string below is accelerated upwards at 20 m/s 2, draw the string and weight forces to scale…

1-20A If the ball on the string below is accelerated upwards at 20 m/s 2, draw the string and weight forces to scale… F g FTFT F T is 3x longer than F g F net = 2x F g

1-25 Type question here. Adjust size & position as necessary.

1-25A Two hockey players are pushing on a puck as it travels across the ice. Their force vectors are shown below. What is the resultant force experienced by the puck? 100 N 130 N F net = √(100 2 + 130 2 ) F net = 164 N F net

2-5 Along which path will the ball move once it hits the gap? 1 2 3

2-5A Path #2 Along which path will the ball move once it hits the gap? 1 2 3

2-10 True or False: It is possible for an object to be moving and still be in equilibrium.

2-10A True or False: It is possible for an object to be moving and still be in equilibrium. True – So long as there is no acceleration or change in motion, the object is in equilibrium (F Net = 0 N). Resistance Pull

2-15 A car on a race track travels around the circular track at a constant speed. Is it in equilibrium?

2-15A A car on a race track travels around the circular track at a constant speed. Is it in equilibrium? No – because in order for the car to move in a circle, there has to be a net force causing a change in the car’s direction.

2-20 You and a friend push a heavy crate across the floor at a constant speed. If you push with a combined force of 100 N, how hard is friction pushing back on the crate? A) less than 100 N B) 100 N exactly C) more than 100 N D) not enough info

2-20A You and a friend push a heavy crate across the floor at a constant speed. If you push with a combined force of 100 N, how hard is friction pushing back on the crate? A) less than 100 N B) 100 N exactly C) more than 100 N D) not enough info F f = 100 N F pull = 100 N

2-25 Suppose you are in an elevator as it accelerates upwards. At that moment, you would feel ________. Why is this?

2-25A Heavier than normal: This is because as the elevator accelerates upwards, you lag behind (due to your inertia), so you feel pressed against the floor harder. Thus, its your reaction to the floor pushing you upward that makes you feel heavier than normal. Suppose you are in an elevator as it accelerates upwards. At that moment, you would feel ________. Why is this? FNFN FgFg

3-5 Two objects (one 10-kg and one 20-kg) are pressed on by the same force. Which one will accelerate more, and by how much?

3-5A The 10-kg object will accelerate by 2x more. Two objects (one 10-kg and one 20-kg) are pressed on by the same force. Which one will accelerate more, and by how much? F = ( 1 / 2 m) (2a) 10 kg F = (2m) ( 1 / 2 a) 20 kg

3-10 What is the weight of a 50-kg object as it falls at a speed of 100 m / sec in a vacuum?

3-10A The speed of the object has no effect on its weight, so… F g = mg = (50 kg)(9.8 m / sec 2 ) F g = 490 Newtons What is the weight of a 50-kg object as it falls at a speed of 100 m / sec in a vacuum? FgFg

3-15 A 2000 kg rocket accelerates through the atmosphere pushed by a thrust of 20,000 N. If the air drag is 18,000 N, then what is the net force acting on it?

3-15A F net = F Thrust – F Drag F net = 20,000 N – 18,000 N F net = 2,000 N A 2000 kg rocket accelerates through the atmosphere pushed by a thrust of 20,000 N. If the air drag is 18,000 N, then what is the net force acting on it? F Drag F Thrust

3-20 A 2000-kg car accelerates down the road. The engine drives it with a force of 5000 N, and friction from the road is 1400 N. What is the car’s acceleration?

3-20A F net = ma and F net = 5000 N – 1400 N So… F net = 3600 N = (2000 kg)a a = 3600 N/2000 kg = 1.8 m / sec 2 A 2000-kg car accelerates down the road. The engine drives it with a force of 5000 N, and friction from the road is 1400 N. What is the car’s acceleration? FfFf F engine

3-25 A 75-kg parachutist is falling through the air – while experiencing an air drag of 200 N. If they fall from rest for 10 seconds in this manner, how fast are they moving?

3-25A A 75-kg parachutist is falling through the air – while experiencing an air drag of 200 N. If they fall from rest for 10 seconds in this manner, how fast are they moving? v = at so we must find a… F net = Weight – Drag = ma So… (75 kg)(9.8 m / s 2 ) – 200 N = (75 kg)a 535 N/75 kg = 7.13 m / s 2 = a v = (7.13 m / s 2 )(10 sec) = 71.3 m / sec FfFf FgFg

4-5 A)greater than B)the same C)less than D)not enough info When you bounce off of a trampoline, the force exerted on you by the trampoline is ______ as compared to the force you exert back on it.

4-5A A)greater than B)the same C)less than D)not enough info When you bounce off of a trampoline, the force exerted on you by the trampoline is ______ as compared to the force you exert back on it.

4-10 What is the reaction force that propels a rocket such as the Space Shuttle? A) the rocket pushing against the launch pad B) the force from the atmosphere C) gravity’s pull from the Earth D) the exhaust gas pushing on the rocket E) not enough info

4-10A What is the reaction force that propels a rocket such as the Space Shuttle? A) the rocket pushing against the launch pad B) the force from the atmosphere C) gravity’s pull from the Earth D) the exhaust gas pushing on the rocket E) not enough info

4-15 A Honda Civic and an 18-wheeler moving at the same speed collide head-on. Which one experiences a greater force of impact?

4-15A They both experience the same force, though the Civic, since it has less mass, will undergo a greater acceleration. A Honda Civic and an 18-wheeler moving at the same speed collide head-on. Which one experiences a greater force of impact?

4-20 Two students, Small Sid and Big Barney, are playing tug-of-war with a rope. Which of them pulls harder on the rope?

4-20A Two students, Small Sid and Big Barney, are playing tug-of-war with a rope. Which of them pulls harder on the rope? Neither pulls harder – they exert equal and opposing forces on the rope.

4-25 A 1-N apple sits on the surface of the Earth. What is the Earth’s weight in reference to this apple? (Note that I’m not asking for the Earth’s mass!)

4-25A The Earth’s weight depends on the object you’re measuring it against. So since the Earth pulls on the apple with a force of 1-N, the apple pulls back A 1-N apple sits on the surface of the Earth. What is the Earth’s weight in reference to this apple? (Note that I’m not asking for the Earth’s mass!) 1 Newton on the Earth gravitationally with a force of 1-N.

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Daily Double Two hockey players are pushing on a puck as it travels across the ice. Their force vectors are shown below. What is the resultant force experienced by the puck? 100 N 130 N

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