1. An 1760 kg car is moving to the right at a constant velocity of 2.94 m/s.
(a) What is the net force on the car?
(b) What would be the net force on the car if it were moving to the left?
2.A freight train has a mass of 6 107 kg. If the locomotive can exert a constant pull of 15 105 N, how long would it take to increase the speed of the train from rest to 85 km/h?
3. Pick the statements below that describe Newton's Second Law. You must pick all the correct answers to get credit.
-If mass increases and force stays the same, acceleration decreases
-Law of inertia
-An object in motion needs a force to keep it moving
-If force increases and mass stays the same, acceleration increases
-For every action, there is an equal but opposite reaction
-An object in motion remains in motion unless acted on by an outside force
-Net force equals zero in equilibrium
-Sum of all forces equals zero in equilibrium
-For every action, there is a reaction in the same direction
-An object at rest remains at rest unless acted on by an outside force
-Fnet=m*a
4.Pick the situations below that fit Newton's Second Law. You must pick all the correct answers to get credit.
-A crate is pushed forward with 60N while friction acts backward with 60N of force
-An airplane is in equilibrium
-The net force on a helicopter is 3,000N
-The forces on a skateboarder are balanced
-A dog pushes down on the ground with 16N of force and the ground pushes up on the dog with 16N of force
-A car accelerates forward at 1.6m/s²
-The forces on an arrow are unbalanced
-A bicycle pushes down on the ground with 67N of force and the ground pushed down on the bicycle with 67N of force.
-A box is pushed forward with 900N and friction acts backwards with 400N of force
-A truck drives at a constant speed of 100m/s
5.Pick the statements below that describe Newton's First Law. You must pick all the correct answers to get credit.
-An object at rest remains at rest unless acted on by an outside force
-If mass increases and force stays the same, acceleration decreases
-Law of inertia
-An object in motion remains in motion unless acted on by an outside force
-For every action, there is an equal but opposite reaction
-For every action, there is a reaction in the same direction
-Sum of all forces equals zero in equilibrium
-An object in motion needs a force to keep it moving
-If force increases and mass stays the same, acceleration increases
-Net force equals zero in equilibrium
-Fnet=m*a
6.Pick the situations below that fit Newton's First Law. You must pick all the correct answers to get credit.
-A crate is pushed forward with 90N while friction acts backward with 90N of force
-The net force on a helicopter is 5,000N
-A box is pushed forward with 700N and friction acts backwards with 400N of force
-A dog pushes down on the ground with 31N of force and the ground pushes up on -the dog with 31N of force
-A car accelerates forward at 3.7m/s²
-The forces on a skateboarder are balanced
-A bicycle pushes down on the ground with 66N of force and the ground pushed down on the bicycle with 66N of force.
-A truck drives at a constant speed of 10m/s
-An airplane is in equilibrium
-The forces on an arrow are unbalanced
3 minutes
1. (a) To find the net force on the car, we can use Newton's Second Law, which states that the net force on an object is equal to the product of its mass and acceleration. However, since the car is moving at a constant velocity, we know that its acceleration is zero. Therefore, the net force on the car is also zero.
(b) If the car were moving to the left at a constant velocity, the situation would be the same as in part (a). Since the car's velocity is constant, its acceleration is zero, and therefore the net force on the car would still be zero.
2. To find the time it takes for the train to increase its speed from rest to 85 km/h, we can use the equation F = ma, where F is the force exerted by the locomotive, m is the mass of the train, and a is the acceleration. In this case, we have F = 15,105 N and m = 6,107 kg. To convert the final velocity of 85 km/h to meters per second, we need to divide by 3.6 (since 1 km/h = 1000 m/3600 s = 1/3.6 m/s). Therefore, the final velocity is 23.61 m/s.
Using the equation F = ma, we can rearrange it to solve for acceleration: a = F/m. Plugging in the values, we have a = (15,105 N)/(6,107 kg) = 2.469 m/s².
Next, we can use the equation v = u + at, where v is the final velocity, u is the initial velocity (which is 0 m/s since the train starts from rest), a is the acceleration, and t is the time. Rearranging the equation to solve for time, we have t = (v - u)/a. Plugging in the values, we have t = (23.61 m/s - 0 m/s)/(2.469 m/s²) = 9.556 s. Therefore, it would take approximately 9.556 seconds to increase the speed of the train from rest to 85 km/h.
3. The correct statements that describe Newton's Second Law are:
- If mass increases and force stays the same, acceleration decreases
- Fnet = ma
4. The situations that fit Newton's Second Law are:
- The crate is pushed forward with 60N while friction acts backward with 60N of force (unbalanced forces)
- The net force on a helicopter is 3,000N (unbalanced force)
- A car accelerates forward at 1.6m/s² (unbalanced force)
5. The correct statements that describe Newton's First Law are:
- An object at rest remains at rest unless acted on by an outside force
- An object in motion remains in motion unless acted on by an outside force
- Law of inertia
6. The situations that fit Newton's First Law are:
- The forces on a skateboarder are balanced (no net force)
- An airplane is in equilibrium (no net force)
- The forces on an arrow are unbalanced (net force acting on it)