1. A 1000kg car moving at 10m/s brakes to a stop in 5s. The average braking force is...........N?
A. 1000
B. 2000
C. 4000
D. 5000
2. A 20kg mass is held 4m above the ground. What is the approximate potential evergy of the mass with respect to the ground?
A. 5J.
B. 50J
C 80J
D. 800J
3. A TV set is pushed a distance of 2m with a force of 20 N that is in the same direcion as the set moves. How mauch work is done on the set?
A. 10J
B. 20J
C. 40J
D. 80J
A. Impulse (Force x time) equals momentum change (velocity x mass)
Solve for the force
B. P.E. = M g H
C. Work = force x distance
You should know these formulas. You can do the calculations in your head.
a
c
d
To solve these questions, we will use relevant equations and concepts from physics. Let's go through each question step by step:
1. The equation we'll be using for this question is Newton's second law of motion: F = ma, where F is the force, m is the mass, and a is the acceleration. To find the average braking force, we need to determine the deceleration.
We can use the equation v = u + at, where v is the final velocity (which is 0 in this case), u is the initial velocity (10 m/s), a is the acceleration, and t is the time (5 seconds).
Rearranging the equation to solve for acceleration, we have:
0 = 10 + a * 5
Simplifying, we get:
-10 = 5a
a = -2 m/s^2
Now, we can substitute the values into the equation F = ma:
F = 1000 kg * -2 m/s^2
F = -2000 N
Since we are looking for the average braking force (ignoring the negative sign), the answer is B. 2000 N.
2. The potential energy (PE) of an object at a certain height is given by the equation PE = m * g * h, where m is the mass, g is the acceleration due to gravity (approximately 9.8 m/s^2 on Earth), and h is the height.
Substituting the given values, we have:
PE = 20 kg * 9.8 m/s^2 * 4m
PE = 784 J
The approximate potential energy of the mass with respect to the ground is therefore D. 800 J.
3. The work done on an object is given by the equation W = F * d, where W is the work done, F is the force, and d is the distance. Since both the force and the distance are given, we can plug in the values into the equation.
W = 20 N * 2 m
W = 40 J
Therefore, the work done on the TV set is C. 40 J.
I hope this explanation helps! Let me know if you have any further questions.